In the last decade, new potential applications of micro- and nano-products in telecommunication, ... more In the last decade, new potential applications of micro- and nano-products in telecommunication, medical diagnostics, photovoltaic, and optoelectronic systems have increased the interest to develop micro-engineering technologies. Injection molding of polymeric materials is a recent method being adapted for serial manufacturing of optic components and packaging at the micro- and nano-scale. Quality assurance of replication into small cavities is an important but underdeveloped factor that is needed to ensure high production efficiency in any micro-fabrication industry. In this work, we introduce a fiber-based interferometric measurement sensor to monitor the cavity filling of optical microstructures fabricated into a macroscopic molding die. The interferometer was capable of resolving melt front motion into the microcavity to the point of complete filling as verified by atomic force microscopy. Despite the low reflectivity of the transparent polymer and unoptimized reflected light co...
The properties of glasses can change significantly as they evolve toward equilibrium. Mechanical ... more The properties of glasses can change significantly as they evolve toward equilibrium. Mechanical deformation appears to influence this physical aging process in conflicting ways, with experiments and simulations showing both effects associated with rejuvenation away from and overaging toward the equilibrium state. Here we report a significant densification effect in a polymer undergoing shear flow under high pressure. We used the high-aspect ratio geometry of the layer compression test to measure the uniform and homogeneous accumulation of plastic strain during isothermal confined compression of a deeply quenched film of polystyrene glass. Combined scanning transmission x-ray microscopy (STXM) and atomic force microscopy confirmed defect-free deformation leaving up to 1.2% residual densification under conditions of confined uniaxial strain. At higher peak strain, plastic shear flow extruded glass from below the compressing punch under conditions of a high background pressure. A further density increase of 2% was observed by STXM for a highly thinned residual thickness of polymer that nevertheless showed no signs of crystallization or internal strain localization. While the confined uniaxial densification can be accounted for by a simple elastic-plastic constitutive model, the high-pressure extrusion densification cannot.
The world is witnessing tumultuous times as major economic powers including the US, UK, Russia, I... more The world is witnessing tumultuous times as major economic powers including the US, UK, Russia, India, and most of Europe continue to be in a state of lockdown. The worst-hit sectors due to this lockdown are sales, production (manufacturing), transport (aerospace and automotive) and tourism. Lockdowns became necessary as a preventive measure to avoid the spread of the contagious and infectious "Coronavirus Disease 2019" (COVID-19). This newly identified disease is caused by a new strain of the virus being referred to as Severe Acute Respiratory Syndrome CoronaVirus 2 (SARS CoV-2; formerly called 2019-nCoV). We review the current medical and manufacturing response to COVID-19, including advances in instrumentation, sensing, use of lasers, fumigation chambers and development of novel tools such as lab-on-the-chip using combinatorial additive and subtractive manufacturing techniques and use of molecular modelling and molecular docking in drug and vaccine discovery. We also offer perspectives on future considerations on climate change, outsourced versus indigenous manufacturing, automation, and antimicrobial resistance. Overall, this paper attempts to identify key areas where manufacturing can be employed to address societal challenges such as COVID-19.
We performed nanomachining combined with photoluminescence spectroscopy to understand the depth d... more We performed nanomachining combined with photoluminescence spectroscopy to understand the depth distribution of nitrogen-vacancy (NV) centers formed by low energy nitrogen ion irradiation of the diamond surface. NVand NV 0 fluorescence signals collected from the surface progressively machined by a diamond tip in an atomic force microscope (AFM) initially rise to a maximum at 5 nm depth before returning to background levels at 10 nm. This maximum corresponds to the defect depth distribution predicted by a SRIM simulation using a 2.5 keV
This review aims to consolidate a scattered literature on the use of a modern nanomechanical test... more This review aims to consolidate a scattered literature on the use of a modern nanomechanical testing techniques in archaeometry materials research such as the process of mummification. It is concluded that nanoindentation tests can provide valuable data about mechanical properties which, in turn, relate to the evolution of ancient biomaterials as well as human history and production methods. As an emerging novel application of an existing technique, some special considerations are warranted for characterization of archaeometry materials. In this review, potential research areas relating to how nanoindentation is expected to benefit and help improve existing practices in archaeometry are identified. These probe new insights into the field and will hopefully raise awareness for use of nanoindentation in world heritage sites.
Atomic simulations are widely used to study the mechanics of small contacts for many contact load... more Atomic simulations are widely used to study the mechanics of small contacts for many contact loading processes such as nanometric cutting, nanoindentation, polishing, grinding and nanoimpact. A common assumption in most such studies is the idealisation of the impacting material (indenter or tool) as a perfectly rigid body. In this study, we explore this idealisation and show that active chemical interactions between two contacting asperities lead to significant deviations of atomic scale contact mechanics from predictions by classical continuum mechanics. We performed a testbed study by simulating velocity-controlled, fixed displacement nanoindentation on single crystal tungsten using five types of indenter (i) a rigid diamond indenter (DI) with full interactions, (ii) a rigid indenter comprising of the atoms of the same material as that of the substrate i.e. tungsten atoms (TI), (iii) a rigid diamond indenter with pairwise attraction turned off, (iv) a deformable diamond indenter and (v) an imaginary, ideally smooth, spherical, rigid and purely repulsive indenter (RI). Corroborating
We use molecular dynamics simulation to study the mechanisms of plasticity during cutting of mono... more We use molecular dynamics simulation to study the mechanisms of plasticity during cutting of monocrystalline and polycrystalline silicon. Three scenarios are considered: (i) cutting a single crystal silicon workpiece with a single crystal diamond tool, (ii) cutting a polysilicon workpiece with a single crystal diamond tool, and (iii) cutting a single crystal silicon workpiece with a polycrystalline diamond tool. A long-range analytical bond order potential is used in the simulations, providing a more accurate picture of the atomic-scale mechanisms of brittle fracture, ductile plasticity, and structural changes in silicon. The MD simulation results show a unique phenomenon of brittle cracking typically inclined at an angle of 45° to 55° to the cut surface, leading to the formation of periodic arrays of nanogrooves in monocrystalline silicon, which is a new insight into previously published results. Furthermore, during cutting, silicon is found to undergo solid-state directional amorphisation without prior Si-I to Si-II (beta tin) transformation, which is in direct contrast to many previously published MD studies on this topic. Our simulations also predict that the propensity for amorphisation is significantly higher in single crystal silicon than in polysilicon, signifying that grain boundaries eases the material removal process.
This data article contains data related to the research article entitled 'Substrate topography: A... more This data article contains data related to the research article entitled 'Substrate topography: A valuable in vitro tool, but a clinical red herring for in vivo tenogenesis' [1]. We report measurements on tenocyte viability, metabolic activity and proliferation on substrates with different topographies. We also report the effect of substrates with different topographies on host cells in a subcutaneous model.
Controlling the cell-substrate interactions at the bio-interface is becoming an inherent element ... more Controlling the cell-substrate interactions at the bio-interface is becoming an inherent element in the design of implantable devices. Modulation of cellular adhesion in vitro, through topographical cues, is a well-documented process that offers control over subsequent cellular functions. However, it is still unclear whether surface topography can be translated into a clinically functional response in vivo at the tissue / device interface. Herein, we demonstrated that anisotropic substrates with a groove depth of ~317 nm and ~1,988 nm promoted human tenocyte alignment parallel to the underlying topography in vitro. However, the rigid poly(lactic-co-glycolic acid) substrates used in this study upregulated the expression of chondrogenic and osteogenic genes, indicating possible tenocyte trans-differentiation. Of significant importance is that none of the topographies assessed (~37 nm, ~317 nm and ~1,988 nm groove depth) induced extracellular matrix orientation parallel to the substrate orientation in a rat patellar tendon model. These data indicate that two-dimensional imprinting technologies are useful tools for in vitro cell phenotype maintenance, rather than for organised neotissue formation in vivo, should multifactorial approaches that consider both surface topography and substrate rigidity be established.
Materials: Chitin squid extract (Industrial Research Ltd-New Zealand) and hexafluoro-2propanol (H... more Materials: Chitin squid extract (Industrial Research Ltd-New Zealand) and hexafluoro-2propanol (HFIP) (Oakwood Products, Inc.) were used as received. Chitin Film Fabrication: Cold-Press (CP): chitin gels were prepared by letting the chitin/HFIP in air for 3-5 days. Then, we put the gels in between the glass slides covered with hardened filter papers (Whatman TM) and press firmly with the help of two clips. Vacuum Drying (VD): The solution of chitin/HFIP was drop cast onto a glass petri dish and let dry in a desiccator connected to the house vacuum. The film was ready after 2-3 days. Vacuum-assisted Filtration (VF): In this method, the solution of chitin/HFIP was drop cast into a porcelain funnel covered the PDMS-coated filter paper. PDMS-coated filter paper was prepared by spin coating PDMS on the filter paper on the speed of 500 rpm for 5 seconds and then 5000 rpm for 1 minute. The resulting fresh PDMS-coated filter papers were dried in the over for 3 hours at 60°C. The porcelain funnel was connected to house vacuum and covered with a glass cover in order to minimize evaporation from the top surface of the chitin film. The drying time for this method was about 1 day. Atomic Force Microscopy: A Veeco Multimode V (Nanoscope IV controller) and Veecoprobes Sb-doped Si cantilevers (ρ = 0.01-0.025 Ω.cm, k = 40 N/m, υ ∼ 300 kHz) were used for atomic force microscopy (AFM).
Anodic Aluminum Oxide (AAO) is widely employed as a template for fabrication of nanowires and nan... more Anodic Aluminum Oxide (AAO) is widely employed as a template for fabrication of nanowires and nanotubes due to its ability to generate self organized (SO), well ordered pore structures. We have developed a new aluminum pre-patterning technique to create well ordered nanopore arrays on thin films deposited on silicon substrates. We form patterns of thicker oxide on the surface via local oxidation process using a conducting Atomic Force Microscope (AFM) tip working in contact mode. Pores are forced to nucleate between the pre-oxidized regions during the anodization process. The relation between applied voltage and ordered interpore distance has been found to be linear for these supported thin films. However, the pore spacing is highly reduced compared to free standing foils. A new empiric law has been confirmed for a wide range of voltages, solution concentrations and different electrolytes, including oxalic and phosphoric acid. Our results show that pre-oxidation patterning is an alt...
We have measured forces between an atomically defined W(111) tip and an Au(111) sample in ultrahi... more We have measured forces between an atomically defined W(111) tip and an Au(111) sample in ultrahigh vacuum at 150 K. The W tips are manipulated and characterized on an atomic scale both before and after sample approach by field ion microscopy. Forces between the tip and the sample are measured by an in situ differential interferometer. We observe strong attractive adhesion forces, which turn repulsive upon the further approach of the tip towards the Au surface. Unexpected for a metallic system, there is no spontaneous jump to contact. The force versus tip-sample distance curve shows only modest hysteresis, and the field ion microscopy images reveal an atomically unchanged tip apex. [S0031-9007(98)06188-2]
UCC Library and UCC researchers have made this item openly available. Please let us know how this... more UCC Library and UCC researchers have made this item openly available. Please let us know how this has helped you. Thanks! Title Mechanical constraint and release generates long, ordered horizontal pores in anodic alumina templates
The mechanical patterning of thin films has received recent attention due to significant potentia... more The mechanical patterning of thin films has received recent attention due to significant potential for efficient nanostructure fabrication. For solid films, mechanically thinning wide areas remains particularly challenging. In this work, we introduce a new plastic ratchet mechanism involving small amplitude (<10 nm), oscillatory shear motion of the forging die. This isothermal mechanism significantly extends mass transport across surfaces, broadening the scope of nanoscale processing for a potentially wide class of solid ductile materials.
Self organizing templates used as etch masks and growth seeds enable efficient mass fabrication o... more Self organizing templates used as etch masks and growth seeds enable efficient mass fabrication of nanoscale device layers. In this work we introduce a new way to direct self-organisation of nanoscale pore formation during anodisation of metal layers of direct relevance to nanofabrication process flows. We demonstrate and quantitatively characterize how proximal surface oxidation frustrates and redirects random pore ordering in the film. Our results show a strict correlation between pore formation and oxide thickness on the aluminum surface providing important information on pore nucleation and growth in substrate-supported thin films and confirming the predictions of several existing theoretical models on pore growth. We find a line ar relation between applied voltage and intrinsic self organizing interpore distance for supported thin films (from 80 to 150 nm) over a wide potential window between 40 and 120 V, mirroring behavior of thicker unsupported foils but with a different coefficient of proportionality. Using this technique, we are able to produce arbitrary and highly regular patterns of pores while manipulating pore pitch up to 20% from the natural spacing. This work demonstrates for the first time how local oxidation can direct self organisation.
This work describes the heat transfer process from a heated microcantilever to a substrate. A pla... more This work describes the heat transfer process from a heated microcantilever to a substrate. A platinum-resistance thermometer with a 140nm width was fabricated on a SiO2-coated silicon substrate. The temperature coefficient of resistance estimated from the measurement was 7×10−4K−1, about one-fifth of the bulk value of platinum. The temperature distribution on the substrate was obtained from the thermometer reading, as the cantilever raster scanned the substrate. Comparison between the measurement and calculation reveals that up to 75% of the cantilever power is directly transferred to the substrate through the air gap. From the force-displacement experiment, the effective tip-specimen contact thermal conductance was estimated to be around 40nW∕K. The findings from this study should help understand the thermal interaction between the heated cantilever and the substrate, which is essential to many nanoscale technologies using heated cantilevers.
We present a new scanning-probe-based data-storage concept called the "millipede" that combines u... more We present a new scanning-probe-based data-storage concept called the "millipede" that combines ultrahigh density, terabit capacity, small form factor, and high data rate. Ultrahigh storage density has been demonstrated by a new thermomechanical local-probe technique to store, read back, and erase data in very thin polymer films. With this new technique, nanometer-sized bit indentations and pitch sizes have been made by a single cantilever/tip into thin polymer layers, resulting in a data storage densities of up to 1 Tb/in 2. High data rates are achieved by parallel operation of large two-dimensional (2-D) atomic force microscope (AFM) arrays that have been batch-fabricated by silicon surface-micromachining techniques. The very large-scale integration (VLSI) of micro/nanomechanical devices (cantilevers/tips) on a single chip leads to the largest and densest 2-D array of 32 32 (1024) AFM cantilevers with integrated write/read/erase storage functionality ever built. Time-multiplexed electronics control the functional storage cycles for parallel operation of the millipede array chip. Initial areal densities of 100-200 Gb/in 2 have been achieved with the 32 32 array chip, which has potential for further improvements. A complete prototype system demonstrating the basic millipede functions has been built, and an integrated five-axis scanner device used in this prototype is described in detail. For millipede storage applications the polymer medium plays a crucial role. Based on a systematic study of different polymers with varying glass-transition temperatures, the underlying physical mechanism of bit writing has been identified, allowing the correlation of polymer properties with millipede-relevant parameters. In addition, a novel erase mechanism has been established that exploits the metastable nature of written bits.
In the last decade, new potential applications of micro- and nano-products in telecommunication, ... more In the last decade, new potential applications of micro- and nano-products in telecommunication, medical diagnostics, photovoltaic, and optoelectronic systems have increased the interest to develop micro-engineering technologies. Injection molding of polymeric materials is a recent method being adapted for serial manufacturing of optic components and packaging at the micro- and nano-scale. Quality assurance of replication into small cavities is an important but underdeveloped factor that is needed to ensure high production efficiency in any micro-fabrication industry. In this work, we introduce a fiber-based interferometric measurement sensor to monitor the cavity filling of optical microstructures fabricated into a macroscopic molding die. The interferometer was capable of resolving melt front motion into the microcavity to the point of complete filling as verified by atomic force microscopy. Despite the low reflectivity of the transparent polymer and unoptimized reflected light co...
The properties of glasses can change significantly as they evolve toward equilibrium. Mechanical ... more The properties of glasses can change significantly as they evolve toward equilibrium. Mechanical deformation appears to influence this physical aging process in conflicting ways, with experiments and simulations showing both effects associated with rejuvenation away from and overaging toward the equilibrium state. Here we report a significant densification effect in a polymer undergoing shear flow under high pressure. We used the high-aspect ratio geometry of the layer compression test to measure the uniform and homogeneous accumulation of plastic strain during isothermal confined compression of a deeply quenched film of polystyrene glass. Combined scanning transmission x-ray microscopy (STXM) and atomic force microscopy confirmed defect-free deformation leaving up to 1.2% residual densification under conditions of confined uniaxial strain. At higher peak strain, plastic shear flow extruded glass from below the compressing punch under conditions of a high background pressure. A further density increase of 2% was observed by STXM for a highly thinned residual thickness of polymer that nevertheless showed no signs of crystallization or internal strain localization. While the confined uniaxial densification can be accounted for by a simple elastic-plastic constitutive model, the high-pressure extrusion densification cannot.
The world is witnessing tumultuous times as major economic powers including the US, UK, Russia, I... more The world is witnessing tumultuous times as major economic powers including the US, UK, Russia, India, and most of Europe continue to be in a state of lockdown. The worst-hit sectors due to this lockdown are sales, production (manufacturing), transport (aerospace and automotive) and tourism. Lockdowns became necessary as a preventive measure to avoid the spread of the contagious and infectious "Coronavirus Disease 2019" (COVID-19). This newly identified disease is caused by a new strain of the virus being referred to as Severe Acute Respiratory Syndrome CoronaVirus 2 (SARS CoV-2; formerly called 2019-nCoV). We review the current medical and manufacturing response to COVID-19, including advances in instrumentation, sensing, use of lasers, fumigation chambers and development of novel tools such as lab-on-the-chip using combinatorial additive and subtractive manufacturing techniques and use of molecular modelling and molecular docking in drug and vaccine discovery. We also offer perspectives on future considerations on climate change, outsourced versus indigenous manufacturing, automation, and antimicrobial resistance. Overall, this paper attempts to identify key areas where manufacturing can be employed to address societal challenges such as COVID-19.
We performed nanomachining combined with photoluminescence spectroscopy to understand the depth d... more We performed nanomachining combined with photoluminescence spectroscopy to understand the depth distribution of nitrogen-vacancy (NV) centers formed by low energy nitrogen ion irradiation of the diamond surface. NVand NV 0 fluorescence signals collected from the surface progressively machined by a diamond tip in an atomic force microscope (AFM) initially rise to a maximum at 5 nm depth before returning to background levels at 10 nm. This maximum corresponds to the defect depth distribution predicted by a SRIM simulation using a 2.5 keV
This review aims to consolidate a scattered literature on the use of a modern nanomechanical test... more This review aims to consolidate a scattered literature on the use of a modern nanomechanical testing techniques in archaeometry materials research such as the process of mummification. It is concluded that nanoindentation tests can provide valuable data about mechanical properties which, in turn, relate to the evolution of ancient biomaterials as well as human history and production methods. As an emerging novel application of an existing technique, some special considerations are warranted for characterization of archaeometry materials. In this review, potential research areas relating to how nanoindentation is expected to benefit and help improve existing practices in archaeometry are identified. These probe new insights into the field and will hopefully raise awareness for use of nanoindentation in world heritage sites.
Atomic simulations are widely used to study the mechanics of small contacts for many contact load... more Atomic simulations are widely used to study the mechanics of small contacts for many contact loading processes such as nanometric cutting, nanoindentation, polishing, grinding and nanoimpact. A common assumption in most such studies is the idealisation of the impacting material (indenter or tool) as a perfectly rigid body. In this study, we explore this idealisation and show that active chemical interactions between two contacting asperities lead to significant deviations of atomic scale contact mechanics from predictions by classical continuum mechanics. We performed a testbed study by simulating velocity-controlled, fixed displacement nanoindentation on single crystal tungsten using five types of indenter (i) a rigid diamond indenter (DI) with full interactions, (ii) a rigid indenter comprising of the atoms of the same material as that of the substrate i.e. tungsten atoms (TI), (iii) a rigid diamond indenter with pairwise attraction turned off, (iv) a deformable diamond indenter and (v) an imaginary, ideally smooth, spherical, rigid and purely repulsive indenter (RI). Corroborating
We use molecular dynamics simulation to study the mechanisms of plasticity during cutting of mono... more We use molecular dynamics simulation to study the mechanisms of plasticity during cutting of monocrystalline and polycrystalline silicon. Three scenarios are considered: (i) cutting a single crystal silicon workpiece with a single crystal diamond tool, (ii) cutting a polysilicon workpiece with a single crystal diamond tool, and (iii) cutting a single crystal silicon workpiece with a polycrystalline diamond tool. A long-range analytical bond order potential is used in the simulations, providing a more accurate picture of the atomic-scale mechanisms of brittle fracture, ductile plasticity, and structural changes in silicon. The MD simulation results show a unique phenomenon of brittle cracking typically inclined at an angle of 45° to 55° to the cut surface, leading to the formation of periodic arrays of nanogrooves in monocrystalline silicon, which is a new insight into previously published results. Furthermore, during cutting, silicon is found to undergo solid-state directional amorphisation without prior Si-I to Si-II (beta tin) transformation, which is in direct contrast to many previously published MD studies on this topic. Our simulations also predict that the propensity for amorphisation is significantly higher in single crystal silicon than in polysilicon, signifying that grain boundaries eases the material removal process.
This data article contains data related to the research article entitled 'Substrate topography: A... more This data article contains data related to the research article entitled 'Substrate topography: A valuable in vitro tool, but a clinical red herring for in vivo tenogenesis' [1]. We report measurements on tenocyte viability, metabolic activity and proliferation on substrates with different topographies. We also report the effect of substrates with different topographies on host cells in a subcutaneous model.
Controlling the cell-substrate interactions at the bio-interface is becoming an inherent element ... more Controlling the cell-substrate interactions at the bio-interface is becoming an inherent element in the design of implantable devices. Modulation of cellular adhesion in vitro, through topographical cues, is a well-documented process that offers control over subsequent cellular functions. However, it is still unclear whether surface topography can be translated into a clinically functional response in vivo at the tissue / device interface. Herein, we demonstrated that anisotropic substrates with a groove depth of ~317 nm and ~1,988 nm promoted human tenocyte alignment parallel to the underlying topography in vitro. However, the rigid poly(lactic-co-glycolic acid) substrates used in this study upregulated the expression of chondrogenic and osteogenic genes, indicating possible tenocyte trans-differentiation. Of significant importance is that none of the topographies assessed (~37 nm, ~317 nm and ~1,988 nm groove depth) induced extracellular matrix orientation parallel to the substrate orientation in a rat patellar tendon model. These data indicate that two-dimensional imprinting technologies are useful tools for in vitro cell phenotype maintenance, rather than for organised neotissue formation in vivo, should multifactorial approaches that consider both surface topography and substrate rigidity be established.
Materials: Chitin squid extract (Industrial Research Ltd-New Zealand) and hexafluoro-2propanol (H... more Materials: Chitin squid extract (Industrial Research Ltd-New Zealand) and hexafluoro-2propanol (HFIP) (Oakwood Products, Inc.) were used as received. Chitin Film Fabrication: Cold-Press (CP): chitin gels were prepared by letting the chitin/HFIP in air for 3-5 days. Then, we put the gels in between the glass slides covered with hardened filter papers (Whatman TM) and press firmly with the help of two clips. Vacuum Drying (VD): The solution of chitin/HFIP was drop cast onto a glass petri dish and let dry in a desiccator connected to the house vacuum. The film was ready after 2-3 days. Vacuum-assisted Filtration (VF): In this method, the solution of chitin/HFIP was drop cast into a porcelain funnel covered the PDMS-coated filter paper. PDMS-coated filter paper was prepared by spin coating PDMS on the filter paper on the speed of 500 rpm for 5 seconds and then 5000 rpm for 1 minute. The resulting fresh PDMS-coated filter papers were dried in the over for 3 hours at 60°C. The porcelain funnel was connected to house vacuum and covered with a glass cover in order to minimize evaporation from the top surface of the chitin film. The drying time for this method was about 1 day. Atomic Force Microscopy: A Veeco Multimode V (Nanoscope IV controller) and Veecoprobes Sb-doped Si cantilevers (ρ = 0.01-0.025 Ω.cm, k = 40 N/m, υ ∼ 300 kHz) were used for atomic force microscopy (AFM).
Anodic Aluminum Oxide (AAO) is widely employed as a template for fabrication of nanowires and nan... more Anodic Aluminum Oxide (AAO) is widely employed as a template for fabrication of nanowires and nanotubes due to its ability to generate self organized (SO), well ordered pore structures. We have developed a new aluminum pre-patterning technique to create well ordered nanopore arrays on thin films deposited on silicon substrates. We form patterns of thicker oxide on the surface via local oxidation process using a conducting Atomic Force Microscope (AFM) tip working in contact mode. Pores are forced to nucleate between the pre-oxidized regions during the anodization process. The relation between applied voltage and ordered interpore distance has been found to be linear for these supported thin films. However, the pore spacing is highly reduced compared to free standing foils. A new empiric law has been confirmed for a wide range of voltages, solution concentrations and different electrolytes, including oxalic and phosphoric acid. Our results show that pre-oxidation patterning is an alt...
We have measured forces between an atomically defined W(111) tip and an Au(111) sample in ultrahi... more We have measured forces between an atomically defined W(111) tip and an Au(111) sample in ultrahigh vacuum at 150 K. The W tips are manipulated and characterized on an atomic scale both before and after sample approach by field ion microscopy. Forces between the tip and the sample are measured by an in situ differential interferometer. We observe strong attractive adhesion forces, which turn repulsive upon the further approach of the tip towards the Au surface. Unexpected for a metallic system, there is no spontaneous jump to contact. The force versus tip-sample distance curve shows only modest hysteresis, and the field ion microscopy images reveal an atomically unchanged tip apex. [S0031-9007(98)06188-2]
UCC Library and UCC researchers have made this item openly available. Please let us know how this... more UCC Library and UCC researchers have made this item openly available. Please let us know how this has helped you. Thanks! Title Mechanical constraint and release generates long, ordered horizontal pores in anodic alumina templates
The mechanical patterning of thin films has received recent attention due to significant potentia... more The mechanical patterning of thin films has received recent attention due to significant potential for efficient nanostructure fabrication. For solid films, mechanically thinning wide areas remains particularly challenging. In this work, we introduce a new plastic ratchet mechanism involving small amplitude (<10 nm), oscillatory shear motion of the forging die. This isothermal mechanism significantly extends mass transport across surfaces, broadening the scope of nanoscale processing for a potentially wide class of solid ductile materials.
Self organizing templates used as etch masks and growth seeds enable efficient mass fabrication o... more Self organizing templates used as etch masks and growth seeds enable efficient mass fabrication of nanoscale device layers. In this work we introduce a new way to direct self-organisation of nanoscale pore formation during anodisation of metal layers of direct relevance to nanofabrication process flows. We demonstrate and quantitatively characterize how proximal surface oxidation frustrates and redirects random pore ordering in the film. Our results show a strict correlation between pore formation and oxide thickness on the aluminum surface providing important information on pore nucleation and growth in substrate-supported thin films and confirming the predictions of several existing theoretical models on pore growth. We find a line ar relation between applied voltage and intrinsic self organizing interpore distance for supported thin films (from 80 to 150 nm) over a wide potential window between 40 and 120 V, mirroring behavior of thicker unsupported foils but with a different coefficient of proportionality. Using this technique, we are able to produce arbitrary and highly regular patterns of pores while manipulating pore pitch up to 20% from the natural spacing. This work demonstrates for the first time how local oxidation can direct self organisation.
This work describes the heat transfer process from a heated microcantilever to a substrate. A pla... more This work describes the heat transfer process from a heated microcantilever to a substrate. A platinum-resistance thermometer with a 140nm width was fabricated on a SiO2-coated silicon substrate. The temperature coefficient of resistance estimated from the measurement was 7×10−4K−1, about one-fifth of the bulk value of platinum. The temperature distribution on the substrate was obtained from the thermometer reading, as the cantilever raster scanned the substrate. Comparison between the measurement and calculation reveals that up to 75% of the cantilever power is directly transferred to the substrate through the air gap. From the force-displacement experiment, the effective tip-specimen contact thermal conductance was estimated to be around 40nW∕K. The findings from this study should help understand the thermal interaction between the heated cantilever and the substrate, which is essential to many nanoscale technologies using heated cantilevers.
We present a new scanning-probe-based data-storage concept called the "millipede" that combines u... more We present a new scanning-probe-based data-storage concept called the "millipede" that combines ultrahigh density, terabit capacity, small form factor, and high data rate. Ultrahigh storage density has been demonstrated by a new thermomechanical local-probe technique to store, read back, and erase data in very thin polymer films. With this new technique, nanometer-sized bit indentations and pitch sizes have been made by a single cantilever/tip into thin polymer layers, resulting in a data storage densities of up to 1 Tb/in 2. High data rates are achieved by parallel operation of large two-dimensional (2-D) atomic force microscope (AFM) arrays that have been batch-fabricated by silicon surface-micromachining techniques. The very large-scale integration (VLSI) of micro/nanomechanical devices (cantilevers/tips) on a single chip leads to the largest and densest 2-D array of 32 32 (1024) AFM cantilevers with integrated write/read/erase storage functionality ever built. Time-multiplexed electronics control the functional storage cycles for parallel operation of the millipede array chip. Initial areal densities of 100-200 Gb/in 2 have been achieved with the 32 32 array chip, which has potential for further improvements. A complete prototype system demonstrating the basic millipede functions has been built, and an integrated five-axis scanner device used in this prototype is described in detail. For millipede storage applications the polymer medium plays a crucial role. Based on a systematic study of different polymers with varying glass-transition temperatures, the underlying physical mechanism of bit writing has been identified, allowing the correlation of polymer properties with millipede-relevant parameters. In addition, a novel erase mechanism has been established that exploits the metastable nature of written bits.
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