The Position-Sensitive Atom Probe (POSAP) has been used to examine a number of InP based quantum ... more The Position-Sensitive Atom Probe (POSAP) has been used to examine a number of InP based quantum well structures in order to elucidate the chemistry and morphology of the interfaces between wells and barrier layers. The interfaces are of critical importance in determining the performance of devices manufactured from such structures. Results have been obtained from three sets of GaInAdInP wells; all the material was grown by Metal-Organic Chemical Vapour Deposition (MOCVD). The information obtained in these observations will be useful in gaining a fuller understanding of the growth processes of these materials, and, because of good agreement with TEM and HREM, in refioing the models used to interpret data obtained with these techniques and with the standard assessment methods of X-ray diffraction and photoluminescence.
Magnetization processes in Alnico alloys depend on details of the microstructure on a very fine s... more Magnetization processes in Alnico alloys depend on details of the microstructure on a very fine scale. In this paper, we report the results of studies carried out in more detail and at higher resolution than any previous study. Field ion microscopy (FIM) and atom probe microanalysis (AP) were used for microstructure studies, and high-voltage electron microscopy (HVEM) for studies of
Nanocrystalline nickel coating was prepared by flexible friction assisted electrodeposition techn... more Nanocrystalline nickel coating was prepared by flexible friction assisted electrodeposition technology in an additive-free Watts bath. The coating consists of massive equiaxial crystals with an average grain size of about 24 nm and exhibits a (111) preferred orientation. The differential scanning calorimetry (DSC) analysis of nanocrystalline nickel demonstrates that the peak temperature of rapid grain growth is about 285.4 °C, and the peak temperature of grain growth towards equilibrium is around 431.5 °C. The isochronous annealing results reveal that abnormal grain growth behavior is not observed in nanocrystalline nickel without sulfur-containing. The thermal stability of the deposition was improved due to its initial microstructure of the as-deposited nickel and a certain amount of annealing nano-twins with low-energy, which reduces the driving force for grain growth. Consequently, the coating shows a low residual tensile stress of about 50 MPa and a high microhardness of HV 400 at the annealing temperature of 450 °C.
Extended abstract of a paper presented at Microscopy and Microanalysis 2006 in Chicago, Illinois,... more Extended abstract of a paper presented at Microscopy and Microanalysis 2006 in Chicago, Illinois, USA, July 30 – August 3, 2005
ABSTRACT The nanocrystalline Fe-Si-B-Nb-Cu alloy, known as FINEMET, is now a well established com... more ABSTRACT The nanocrystalline Fe-Si-B-Nb-Cu alloy, known as FINEMET, is now a well established commercial soft magnetic material exhibiting excellent permeability while maintaining a high saturation magnetization. It is produced by melt-spinning to form a ribbon with an amorphous structure. The purpose of this investigation was to use 3-dimensional atom probe microanalysis to experimentally quantify the local phase chemistries of this nanocomposite microstructure, with particular reference to the partitioning behavior of the Al.
Proceedings, annual meeting, Electron Microscopy Society of America, 1990
The fabrication of multilayer films (MLF) with layer thicknesses down to one monolayer has led to... more The fabrication of multilayer films (MLF) with layer thicknesses down to one monolayer has led to the development of materials with unique properties not found in bulk materials. The properties of interest depend critically on the structure and composition of the films, with the interfacial regions between the layers being of particular importance. There are a number of magnetic MLF systems based on Co, several of which have potential applications as perpendicular magnetic (e.g Co/Cr) or magneto-optic (e.g. Co/Pt) recording media. Of particular concern are the effects of parameters such as crystallographic texture and interface roughness, which are determined by the fabrication conditions, on magnetic properties and structure.In this study we have fabricated Co-based MLF by UHV thermal evaporation in the prechamber of an atom probe field-ion microscope (AP). The multilayers were deposited simultaneously onto cobalt field-ion specimens (for AP and position-sensitive atom probe (POSAP...
Proceedings, annual meeting, Electron Microscopy Society of America, 1990
The position sensitive atom probe (POSAP), described briefly elsewhere in these proceedings, perm... more The position sensitive atom probe (POSAP), described briefly elsewhere in these proceedings, permits both chemical and spatial information in three dimensions to be recorded from a small volume of material. This technique is particularly applicable to situations where there are fine scale variations in composition present in the material under investigation. We report the application of the POSAP to the characterisation of semiconductor multiple quantum wells and metallic multilayers.The application of devices prepared from quantum well materials depends on the ability to accurately control both the quantum well composition and the quality of the interfaces between the well and barrier layers. A series of metal organic chemical vapour deposition (MOCVD) grown GaInAs-InP quantum wells were examined after being prepared under three different growth conditions. These samples were observed using the POSAP in order to study both the composition of the wells and the interface morphology. ...
The atom probe field-ion microscope has been used to study the diffusion at interfaces in metalli... more The atom probe field-ion microscope has been used to study the diffusion at interfaces in metallic multilayers deposited directly onto field-ion specimens and to develop models for the solid state reactions occuring at the atomic-scale in multilayer systems. Results are presented for the low temperature annealing of a Co-Ni multilayer. Intermixing over about 2 atomic planes is found even in as-deposited samples, extending to mnm after heating at 300°C for 1 hour. Using atom probe results from bulk alloys, a Monte Carlo simulation has been developed for the Fe-Cr system, in which a miscibility gap exists, and is being used in an attempt to model the behaviour of interfaces in Fe-Cr multilayers. Preliminary results are presented, showing that interfaces which are initially mixed over 10 atomic planes become sharper by an ‘interface spinodal’ reaction.
-Des spécimens d'Alnico5 et 7 ont été étudiés avec l'aide de la microscopie ionique dechamp, de l... more -Des spécimens d'Alnico5 et 7 ont été étudiés avec l'aide de la microscopie ionique dechamp, de la microanalyse parsonde atomique et de la microscopie électronique haute tension. La composition et la morphologie des phases ont été déterminées avec précision. Ces résultats ont montré que les changements d'aimantation sont produits par le mouvement "Bloch wall".
Digest of INTERMAG 2003. International Magnetics Conference (Cat. No.03CH37401)
ABSTRACT Perpendicular magnetic recording is being considered as an important candidate for achie... more ABSTRACT Perpendicular magnetic recording is being considered as an important candidate for achieving extremely high density magnetic recording with high thermal stability. One set of materials being most widely studied for this application are Co/Pd and Co/Pt multilayer films. A series of Co/Pd multilayer films, seeded with a Ti-based bilayer seed, were deposited on Si wafers that had been patterned into posts of about 3 micron diameter. Following deposition the posts were patterned using a focus ion beam (FIB) system to form the needle-shaped samples required for 3DAP analysis. The atomic scale composition distribution was characterised using 3DAP, and HREM was used to characterise the atomic scale structure of the films.
Digest of INTERMAG 2003. International Magnetics Conference (Cat. No.03CH37401)
ABSTRACT We discuss the giant magnetoresistance (GMR) property of CoFe/Cu magnetic multilayers. T... more ABSTRACT We discuss the giant magnetoresistance (GMR) property of CoFe/Cu magnetic multilayers. TEM images of the Co/Pt multilayer film show the crystal structure in the layers.
2006 19th International Vacuum Nanoelectronics Conference, 2006
Focused ion beam (FIB) milling has been successfully used to prepare a range of atom probe specim... more Focused ion beam (FIB) milling has been successfully used to prepare a range of atom probe specimens from metal alloys at site specific locations such as grain boundaries, thin ribbons, powders, and multilayer film materials. Commonly employed, 3-step process generates ledges that act as a stress concentration sites at the shank of the specimens. Smoother shank profile of the specimen is therefore desirable, so as to reduce the chance of specimen failure at such points. In this work, an improved method to fabricate the specimens from planar multilayer thin films was presented. The films were deposited onto etched Si posts, prepared by the lithographic patterning of a Si wafer. Capping layers (e.g. Cu, Ni, and Fe) were deposited on top to protect the films of interest from implantation damage caused by the high energy ion beams. Individual posts were attached to the tip of sharpened metal wires, and subsequently sharpened by ion milling in a FEI FIB 200 instrument without further Pt deposition required
ABSTRACTThe study of phase transformations involves making assumptions about interfaces within a ... more ABSTRACTThe study of phase transformations involves making assumptions about interfaces within a material in order to apply mathematical models. An example of this is the Gibbs classical theory of nucleation and growth which is based upon the assumption that the precipitate / matrix interface is sharp. Recent developments in atom probe microscopy have made it possible for the first time to characterize complex three-dimensional internal interfaces within materials to sub-nanometre accuracy. We have used the OPoSAP (Optical Position Sensitive Atom Probe) to characterize the precipitate / matrix interface in the dilute Cu-Co system which is a model alloy for the study of homogeneous nucleation and growth. Interface widths derived from radial composition profiles were measured to be 0.9 ± 0.2 nm in size. The effects of thermal energy, positioning inaccuracies, and statistical limitations on the measurement of interface widths are examined through the use of mathematical models and comp...
2006 19th International Vacuum Nanoelectronics Conference, 2006
... Vessel Steels G. Shal*, S. Hirosawa2, A. MorleyI, A. Cerezol, GDW Smith', D. Ellis3 and ... more ... Vessel Steels G. Shal*, S. Hirosawa2, A. MorleyI, A. Cerezol, GDW Smith', D. Ellis3 and T Williams3 2 ... DE21 7XX * Corresponding author: tel: +44 1865 273711, fax: +44 1865 273789, e-mail:[email protected]. Grain ...
We have recently suggested a novel method for improving mass resolution in the scanning atom prob... more We have recently suggested a novel method for improving mass resolution in the scanning atom probe (SAP), based on a post-deceleration scheme. A two-conductor counter electrode is used, and the high voltage pulse is applied to the front conductor, with the rear conductor being held at ground. For a separation between the two conductors of 100 mm or less, ions travel between the two while the pulse is essentially constant, so that the ion leaves the counter electrode with an energy equivalent to the applied d.c. potential. In this paper, we have used a numerical model for the electric fields in the SAP to verify the results of the simpler analytical approach used earlier. In particular, the ion acceleration in the vicinity of the tip, previously assumed to be instantaneous, was modelled using a hyperboloidal field approximation. The numerical model was used to calculate the flight time for ions having a range of masses and evaporating over a range of times at the peak of a high voltage pulse. Modelled mass resolutions, calculated in this way, were then compared with analytical expressions, and were found to agree very well. This shows that the earlier assumption of an instantaneous acceleration did not seriously affect the validity of the approach.
An electrostatic field and ion trajectory program has been used to characterise the focussing beh... more An electrostatic field and ion trajectory program has been used to characterise the focussing behaviour of simple einzel lenses used in linear flight-path atom probe designs. The focussing power and spot size obtained for two basic lens designs have been found as a function of applied voltage and lens size. A simple model for the beana convergence generated by such a lens has been used to calculate the time resolution and spatial focussing of a combined system including einzel lens and toroidal sector energy compensator. The results of these calculations agree well with the observed performance in a high resolution energy compensated atom probe. We find that the lens is able to improve the time resolution of a poorly focussed toroidal sector, but only on one side of the correct focussing condition. Under these conditions. accurate spatial focussing will not be achieved.
The Position-Sensitive Atom Probe (POSAP) has been used to examine a number of InP based quantum ... more The Position-Sensitive Atom Probe (POSAP) has been used to examine a number of InP based quantum well structures in order to elucidate the chemistry and morphology of the interfaces between wells and barrier layers. The interfaces are of critical importance in determining the performance of devices manufactured from such structures. Results have been obtained from three sets of GaInAdInP wells; all the material was grown by Metal-Organic Chemical Vapour Deposition (MOCVD). The information obtained in these observations will be useful in gaining a fuller understanding of the growth processes of these materials, and, because of good agreement with TEM and HREM, in refioing the models used to interpret data obtained with these techniques and with the standard assessment methods of X-ray diffraction and photoluminescence.
Magnetization processes in Alnico alloys depend on details of the microstructure on a very fine s... more Magnetization processes in Alnico alloys depend on details of the microstructure on a very fine scale. In this paper, we report the results of studies carried out in more detail and at higher resolution than any previous study. Field ion microscopy (FIM) and atom probe microanalysis (AP) were used for microstructure studies, and high-voltage electron microscopy (HVEM) for studies of
Nanocrystalline nickel coating was prepared by flexible friction assisted electrodeposition techn... more Nanocrystalline nickel coating was prepared by flexible friction assisted electrodeposition technology in an additive-free Watts bath. The coating consists of massive equiaxial crystals with an average grain size of about 24 nm and exhibits a (111) preferred orientation. The differential scanning calorimetry (DSC) analysis of nanocrystalline nickel demonstrates that the peak temperature of rapid grain growth is about 285.4 °C, and the peak temperature of grain growth towards equilibrium is around 431.5 °C. The isochronous annealing results reveal that abnormal grain growth behavior is not observed in nanocrystalline nickel without sulfur-containing. The thermal stability of the deposition was improved due to its initial microstructure of the as-deposited nickel and a certain amount of annealing nano-twins with low-energy, which reduces the driving force for grain growth. Consequently, the coating shows a low residual tensile stress of about 50 MPa and a high microhardness of HV 400 at the annealing temperature of 450 °C.
Extended abstract of a paper presented at Microscopy and Microanalysis 2006 in Chicago, Illinois,... more Extended abstract of a paper presented at Microscopy and Microanalysis 2006 in Chicago, Illinois, USA, July 30 – August 3, 2005
ABSTRACT The nanocrystalline Fe-Si-B-Nb-Cu alloy, known as FINEMET, is now a well established com... more ABSTRACT The nanocrystalline Fe-Si-B-Nb-Cu alloy, known as FINEMET, is now a well established commercial soft magnetic material exhibiting excellent permeability while maintaining a high saturation magnetization. It is produced by melt-spinning to form a ribbon with an amorphous structure. The purpose of this investigation was to use 3-dimensional atom probe microanalysis to experimentally quantify the local phase chemistries of this nanocomposite microstructure, with particular reference to the partitioning behavior of the Al.
Proceedings, annual meeting, Electron Microscopy Society of America, 1990
The fabrication of multilayer films (MLF) with layer thicknesses down to one monolayer has led to... more The fabrication of multilayer films (MLF) with layer thicknesses down to one monolayer has led to the development of materials with unique properties not found in bulk materials. The properties of interest depend critically on the structure and composition of the films, with the interfacial regions between the layers being of particular importance. There are a number of magnetic MLF systems based on Co, several of which have potential applications as perpendicular magnetic (e.g Co/Cr) or magneto-optic (e.g. Co/Pt) recording media. Of particular concern are the effects of parameters such as crystallographic texture and interface roughness, which are determined by the fabrication conditions, on magnetic properties and structure.In this study we have fabricated Co-based MLF by UHV thermal evaporation in the prechamber of an atom probe field-ion microscope (AP). The multilayers were deposited simultaneously onto cobalt field-ion specimens (for AP and position-sensitive atom probe (POSAP...
Proceedings, annual meeting, Electron Microscopy Society of America, 1990
The position sensitive atom probe (POSAP), described briefly elsewhere in these proceedings, perm... more The position sensitive atom probe (POSAP), described briefly elsewhere in these proceedings, permits both chemical and spatial information in three dimensions to be recorded from a small volume of material. This technique is particularly applicable to situations where there are fine scale variations in composition present in the material under investigation. We report the application of the POSAP to the characterisation of semiconductor multiple quantum wells and metallic multilayers.The application of devices prepared from quantum well materials depends on the ability to accurately control both the quantum well composition and the quality of the interfaces between the well and barrier layers. A series of metal organic chemical vapour deposition (MOCVD) grown GaInAs-InP quantum wells were examined after being prepared under three different growth conditions. These samples were observed using the POSAP in order to study both the composition of the wells and the interface morphology. ...
The atom probe field-ion microscope has been used to study the diffusion at interfaces in metalli... more The atom probe field-ion microscope has been used to study the diffusion at interfaces in metallic multilayers deposited directly onto field-ion specimens and to develop models for the solid state reactions occuring at the atomic-scale in multilayer systems. Results are presented for the low temperature annealing of a Co-Ni multilayer. Intermixing over about 2 atomic planes is found even in as-deposited samples, extending to mnm after heating at 300°C for 1 hour. Using atom probe results from bulk alloys, a Monte Carlo simulation has been developed for the Fe-Cr system, in which a miscibility gap exists, and is being used in an attempt to model the behaviour of interfaces in Fe-Cr multilayers. Preliminary results are presented, showing that interfaces which are initially mixed over 10 atomic planes become sharper by an ‘interface spinodal’ reaction.
-Des spécimens d'Alnico5 et 7 ont été étudiés avec l'aide de la microscopie ionique dechamp, de l... more -Des spécimens d'Alnico5 et 7 ont été étudiés avec l'aide de la microscopie ionique dechamp, de la microanalyse parsonde atomique et de la microscopie électronique haute tension. La composition et la morphologie des phases ont été déterminées avec précision. Ces résultats ont montré que les changements d'aimantation sont produits par le mouvement "Bloch wall".
Digest of INTERMAG 2003. International Magnetics Conference (Cat. No.03CH37401)
ABSTRACT Perpendicular magnetic recording is being considered as an important candidate for achie... more ABSTRACT Perpendicular magnetic recording is being considered as an important candidate for achieving extremely high density magnetic recording with high thermal stability. One set of materials being most widely studied for this application are Co/Pd and Co/Pt multilayer films. A series of Co/Pd multilayer films, seeded with a Ti-based bilayer seed, were deposited on Si wafers that had been patterned into posts of about 3 micron diameter. Following deposition the posts were patterned using a focus ion beam (FIB) system to form the needle-shaped samples required for 3DAP analysis. The atomic scale composition distribution was characterised using 3DAP, and HREM was used to characterise the atomic scale structure of the films.
Digest of INTERMAG 2003. International Magnetics Conference (Cat. No.03CH37401)
ABSTRACT We discuss the giant magnetoresistance (GMR) property of CoFe/Cu magnetic multilayers. T... more ABSTRACT We discuss the giant magnetoresistance (GMR) property of CoFe/Cu magnetic multilayers. TEM images of the Co/Pt multilayer film show the crystal structure in the layers.
2006 19th International Vacuum Nanoelectronics Conference, 2006
Focused ion beam (FIB) milling has been successfully used to prepare a range of atom probe specim... more Focused ion beam (FIB) milling has been successfully used to prepare a range of atom probe specimens from metal alloys at site specific locations such as grain boundaries, thin ribbons, powders, and multilayer film materials. Commonly employed, 3-step process generates ledges that act as a stress concentration sites at the shank of the specimens. Smoother shank profile of the specimen is therefore desirable, so as to reduce the chance of specimen failure at such points. In this work, an improved method to fabricate the specimens from planar multilayer thin films was presented. The films were deposited onto etched Si posts, prepared by the lithographic patterning of a Si wafer. Capping layers (e.g. Cu, Ni, and Fe) were deposited on top to protect the films of interest from implantation damage caused by the high energy ion beams. Individual posts were attached to the tip of sharpened metal wires, and subsequently sharpened by ion milling in a FEI FIB 200 instrument without further Pt deposition required
ABSTRACTThe study of phase transformations involves making assumptions about interfaces within a ... more ABSTRACTThe study of phase transformations involves making assumptions about interfaces within a material in order to apply mathematical models. An example of this is the Gibbs classical theory of nucleation and growth which is based upon the assumption that the precipitate / matrix interface is sharp. Recent developments in atom probe microscopy have made it possible for the first time to characterize complex three-dimensional internal interfaces within materials to sub-nanometre accuracy. We have used the OPoSAP (Optical Position Sensitive Atom Probe) to characterize the precipitate / matrix interface in the dilute Cu-Co system which is a model alloy for the study of homogeneous nucleation and growth. Interface widths derived from radial composition profiles were measured to be 0.9 ± 0.2 nm in size. The effects of thermal energy, positioning inaccuracies, and statistical limitations on the measurement of interface widths are examined through the use of mathematical models and comp...
2006 19th International Vacuum Nanoelectronics Conference, 2006
... Vessel Steels G. Shal*, S. Hirosawa2, A. MorleyI, A. Cerezol, GDW Smith', D. Ellis3 and ... more ... Vessel Steels G. Shal*, S. Hirosawa2, A. MorleyI, A. Cerezol, GDW Smith', D. Ellis3 and T Williams3 2 ... DE21 7XX * Corresponding author: tel: +44 1865 273711, fax: +44 1865 273789, e-mail:[email protected]. Grain ...
We have recently suggested a novel method for improving mass resolution in the scanning atom prob... more We have recently suggested a novel method for improving mass resolution in the scanning atom probe (SAP), based on a post-deceleration scheme. A two-conductor counter electrode is used, and the high voltage pulse is applied to the front conductor, with the rear conductor being held at ground. For a separation between the two conductors of 100 mm or less, ions travel between the two while the pulse is essentially constant, so that the ion leaves the counter electrode with an energy equivalent to the applied d.c. potential. In this paper, we have used a numerical model for the electric fields in the SAP to verify the results of the simpler analytical approach used earlier. In particular, the ion acceleration in the vicinity of the tip, previously assumed to be instantaneous, was modelled using a hyperboloidal field approximation. The numerical model was used to calculate the flight time for ions having a range of masses and evaporating over a range of times at the peak of a high voltage pulse. Modelled mass resolutions, calculated in this way, were then compared with analytical expressions, and were found to agree very well. This shows that the earlier assumption of an instantaneous acceleration did not seriously affect the validity of the approach.
An electrostatic field and ion trajectory program has been used to characterise the focussing beh... more An electrostatic field and ion trajectory program has been used to characterise the focussing behaviour of simple einzel lenses used in linear flight-path atom probe designs. The focussing power and spot size obtained for two basic lens designs have been found as a function of applied voltage and lens size. A simple model for the beana convergence generated by such a lens has been used to calculate the time resolution and spatial focussing of a combined system including einzel lens and toroidal sector energy compensator. The results of these calculations agree well with the observed performance in a high resolution energy compensated atom probe. We find that the lens is able to improve the time resolution of a poorly focussed toroidal sector, but only on one side of the correct focussing condition. Under these conditions. accurate spatial focussing will not be achieved.
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Papers by Alfred Cerezo