Journal Articles by Gang Zhang
Based on the non-equilibrium molecular dynamics simulations, we have studied the thermal conducti... more Based on the non-equilibrium molecular dynamics simulations, we have studied the thermal conductivities of a novel ultra-thin one-dimensional carbon nanomaterial e diamond nanothread (DNT). Unlike single-wall carbon nanotube (CNT), the existence of the Stone-Wales (SW) transformations in DNT endows it with richer thermal transport characteristics. There is a transition from wave-dominated to particle-dominated transport region, which depends on the length of poly-benzene rings. However, independent of the transport region, strong length dependence in thermal conductivity is observed in DNTs with different lengths of poly-benzene ring. The distinctive SW characteristic in DNT provides more to tune the thermal conductivity not found in the homogeneous structure of CNT. Therefore, DNT is an ideal platform to investigate various thermal transport mechanisms at the nanoscale. Its high tunability raises the potential to design DNTs for different applications, such as thermal connection and temperature management.
Papers by Gang Zhang
Journal of Physics D: Applied Physics, 2014
ABSTRACT Using the nonequilibrium Green's function method, we investigate the effects of ... more ABSTRACT Using the nonequilibrium Green's function method, we investigate the effects of edge reconstructions on the thermal conductance of graphene nanoribbons (GNRs). For the first time, we show that the thermal conductance of edge reconstructed zigzag GNRs oscillates with the number of dimers along the width direction, N. When N is an odd or even number, the thermal conductance of edge reconstructed zigzag GNRs is about 25 or 85% that of the perfect zigzag GNRs, respectively. For edge reconstructed armchair GNRs, the thermal conductance only decreases slightly and it changes linearly with N. The significant difference in the width dependence of GNR thermal conductance may be attributed to the topological symmetry and edge reconstruction of GNRs. Our results shed light on a new approach to control the thermal conductance of GNRs by reconstructing their edges and controlling their topological symmetry.
Fluctuation Relations and Beyond, 2013
Thermal transport in nanoscale structures has attracted an increasing attention in last two decad... more Thermal transport in nanoscale structures has attracted an increasing attention in last two decades. Here we give a brief review of the recent developments in experimental and theoretical studies of heat transport in nano materials such as nanotube and nanowire. In particular, we will demonstrate that the phonons in nanotube and nanowires transport super-diffusively, which leads to a length dependent thermal conductivity. In other words, heat conduction in low dimensional nanostructures does not obey the Fourier's law.
Scientific reports, Jan 20, 2014
Using first-principles calculations, we study the electronic properties of few-layer phosphorene ... more Using first-principles calculations, we study the electronic properties of few-layer phosphorene focusing on layer-dependent behavior of band gap, work function band alignment and carrier effective mass. It is found that few-layer phosphorene shows a robust direct band gap character, and its band gap decreases with the number of layers following a power law. The work function decreases rapidly from monolayer (5.16 eV) to trilayer (4.56 eV), and then slowly upon further increasing the layer number. Compared to monolayer phosphorene, there is a drastic decrease of hole effective mass along the ridge (zigzag) direction for bilayer phosphorene, indicating a strong interlayer coupling and screening effect. Our study suggests that 1). Few-layer phosphorene with a layer-dependent band gap and a robust direct band gap character is promising for efficient solar energy harvest. 2). Few-layer phosphorene outperforms monolayer counterpart in terms of a lighter carrier effective mass, a higher c...
AIP Advances, 2012
This review summarizes recent studies of thermal transport in nanoscaled semiconductors. Differen... more This review summarizes recent studies of thermal transport in nanoscaled semiconductors. Different from bulk materials, new physics and novel thermal properties arise in low dimensional nanostructures, such as the abnormal heat conduction, the size dependence of thermal conductivity, phonon boundary/edge scatterings. It is also demonstrated that phonons transport super-diffusively in low dimensional structures, in other words, Fourier's law is not applicable. Based on manipulating phonons, we also discuss envisioned applications of nanostructures in a broad area, ranging from thermoelectrics, heat dissipation to phononic devices.
Transactions of Nonferrous Metals Society of China, 2007
Transactions of Nonferrous Metals Society of China www.csu.edu.cn/ysx b/ Effect of adding methods... more Transactions of Nonferrous Metals Society of China www.csu.edu.cn/ysx b/ Effect of adding methods of metallic phase on microstructure and thermal shock resistance of Ni/(90NiFe204-1 ONiO) cermets LA1 Yan-qing(@a.%), ZHANG Yong(% s), TIAN Zhong-liang(El !&" p), SUN Xiao-gang(.S/l\/J\ Ply), ZHANG Gang(% Hq), LI Jie(% 8
Nanoscale, 2010
The influence of doping on the device characteristics of In 0.5 Ga 0.5 As/GaAs/Al 0.2 Ga 0.8 As q... more The influence of doping on the device characteristics of In 0.5 Ga 0.5 As/GaAs/Al 0.2 Ga 0.8 As quantum dots-in-awell infrared photodetectors
Nano Today, 2010
We study heat conduction and diffusion in silicon nanowires (SiNWs) systematically by using non-e... more We study heat conduction and diffusion in silicon nanowires (SiNWs) systematically by using non-equilibrium molecular dynamics. It is found that the thermal conductivity (κ) of SiNWs diverges with the length as, β κ L ∝ , even when the length is up to 1.1 μm which is much longer than the phonon mean free path. The dependences of β on temperature and length are also discussed. Moreover, an anomalous heat diffusion is observed which is believed to be responsible for the length dependent thermal conductivity. Our results provide strong evidence that Fourier's law of heat conduction is not valid in low dimensional nanostructures.
Nano Letters, 2008
The thermal conductivity of silicon nanowires (SiNWs) is investigated by molecular dynamics (MD) ... more The thermal conductivity of silicon nanowires (SiNWs) is investigated by molecular dynamics (MD) simulation. It is found that the thermal conductivity of SiNWs can be reduced exponentially by isotopic defects at room temperature. The thermal conductivity reaches the minimum, which is about 27% of that of pure 28 Si NW, when doped with fifty percent isotope atoms. The thermal conductivity of isotopic-superlattice structured SiNWs depends clearly on the period of superlattice. At a critical period of 1.09 nm, the thermal conductivity is only 25% of the value of pure Si NW. An anomalous enhancement of thermal conductivity is observed when the superlattice period is smaller than this critical length. The ultra-low thermal conductivity of superlattice structured SiNWs is explained with phonon spectrum theory. Silicon nanowires (SiNWs) have attracted a great attention in recent years because of their excellent electrical and mechanical properties [1] and their potential applications in many areas including biosensor.[2] SiNWs are appealing choice because of their ideal interface compatibility with conventional Si-based technology [3, 4]. It is found that the electronic property of SiNWs depends on the surface and growth direction significantly. The band gap is found to be decreased with increasing diameter. [5, 6] These special properties are partially due to the quantum confinement effects in nano materials. On the other hand, like some other nano materials, the silicon nanowires might be used as thermoelectric materials.
Journal of the Physical Society of Japan, 2010
We investigate systematically the impacts of heat bath used in molecular dynamics simulations on ... more We investigate systematically the impacts of heat bath used in molecular dynamics simulations on heat conduction in nanostructures exemplified by Silicon Nanowires (SiNWs) and Silicon/Germanium nano junction. It is found that multiple layers of Nosé-Hoover heat bath are required to reduce the temperature jump at the boundary, while only a single layer of Langevin heat bath is sufficient to generate a linear temperature profile with small boundary temperature jump. Moreover, an intermediate value of heat bath parameter is recommended for both Nosé-Hoover and Langevin heat bath in order to achieve correct temperature profile and thermal conductivity in homogeneous materials. Furthermore, the thermal rectification ratio in Si/Ge thermal diode depends on the choice of Nosé-Hoover heat bath parameter remarkably, which may lead to non-physical results. In contrast, Langevin heat bath is recommended because it can produce consistent results with experiment in large heat bath parameter range.
Journal of Applied Physics, 2012
Silicon dioxide and silicon (SiO 2 /Si) interface plays a very important role in semiconductor in... more Silicon dioxide and silicon (SiO 2 /Si) interface plays a very important role in semiconductor industry. However, at nanoscale, its interfacial thermal properties haven't been well understood so far. In this paper, we systematically study the interfacial thermal resistance (Kapitza resistance) of a heterojunction composed of amorphous silicon dioxide and crystalline silicon by using molecular dynamics simulations. Numerical results have shown that Kapitza resistance at SiO 2 /Si interface depends on the interfacial coupling strength remarkably. In the weak interfacial coupling limit, Kapitza resistance depends on both the detailed interfacial structure and the length of the heterojunction, showing large fluctuation among different 2 samples. In contrast, it is almost insensitive to the detailed interfacial structure or the length of the heterojunction in the strong interfacial coupling limit, giving rise to a nearly constant value around 0.9×10-9 m 2 KW-1 at room temperature. Moreover, the temperature dependent Kapitza resistance in the strong interfacial coupling limit has also been examined. Our study provides useful guidance to the thermal management and heat dissipation across nanoscale SiO 2 /Si interface, in particular for the design of silicon nanowire based nano electronics and photonics devices.
Chaos: An Interdisciplinary Journal of Nonlinear Science, 2005
We study anomalous heat conduction and anomalous diffusion in low-dimensional systems ranging fro... more We study anomalous heat conduction and anomalous diffusion in low-dimensional systems ranging from nonlinear lattices, single walled carbon nanotubes, to billiard gas channels. We find that in all discussed systems, the anomalous heat conductivity can be connected with the anomalous diffusion, namely, if energy diffusion is 2 ͑t͒ =2Dt ␣ ͑0 Ͻ ␣ ഛ 2͒, then the thermal conductivity can be expressed in terms of the system size L as = cL  with  =2−2/␣. This result predicts that a normal diffusion ͑␣ =1͒ implies a normal heat conduction obeying the Fourier law ͑ =0͒, a superdiffusion ͑␣ Ͼ 1͒ implies an anomalous heat conduction with a divergent thermal conductivity ͑ Ͼ 0͒, and more interestingly, a subdiffusion ͑␣ Ͻ 1͒ implies an anomalous heat conduction with a convergent thermal conductivity ͑ Ͻ 0͒, consequently, the system is a thermal insulator in the thermodynamic limit. Existing numerical data support our theoretical prediction.
Journal of Central South University of Technology, 2007
Densification and sintering dynamics of 10NiO-NiFe 2 O 4 composites doped with CaO LI Jie(李 劼), Z... more Densification and sintering dynamics of 10NiO-NiFe 2 O 4 composites doped with CaO LI Jie(李 劼), ZHANG Gang(张 刚), LAI Yan-qing(赖延清), ZHANG Yong(张 勇), TIAN Zhong-liang(田忠良)
Applied Physics Letters, 2009
In this paper, heat flux in graphene nano ribbons has been studied by using molecular dynamics si... more In this paper, heat flux in graphene nano ribbons has been studied by using molecular dynamics simulations. It is found that the heat flux runs preferentially along the direction of decreasing width, which demonstrates significant thermal rectification effect in the asymmetric graphene ribbons. The dependence of rectification ratio on the vertex angle and the length are also discussed. Compared to the carbon nanotube based onedimensional thermal rectifier, graphene nano ribbons have much higher rectification ratio even in large scale. Our results demonstrate that asymmetric graphene ribbon might be a promising structure for practical thermal (phononics) device.
Applied Physics Letters, 2008
With molecular dynamics simulations, we demonstrate that the carbon nanocone is an excellent ther... more With molecular dynamics simulations, we demonstrate that the carbon nanocone is an excellent thermal rectifier. Obvious thermal rectification ratio in large temperature range, from 200K to 400K, has been observed. Furthermore, the rectification of nanocone does not depend on the length very sensitively, which is in stark contrast with the nanotube thermal rectifier in which the rectification decreases dramatically as the length increases. In nanocone, the heat flux is controlled by match/mismatch of the phonon power spectra. Our work demonstrates that carbon nanocone is a promising practical phononic device.
Applied Physics Letters, 2014
We reported the thermal conductivity of the two-dimensional carbon nanotube (CNT)-based architect... more We reported the thermal conductivity of the two-dimensional carbon nanotube (CNT)-based architecture, which can be constructed through welding of single-wall CNTs by electron beam. Using large-scale nonequilibrium molecular dynamics simulations, the thermal conductivity is found to vary with different junction types due to their different phonon scatterings at the junction. The strong length and strain dependence of the thermal conductivity suggests an effective avenue to tune the thermal transport properties of the CNT-based architecture, benefiting the design of nanoscale thermal rectifiers or phonon engineering.
Uploads
Journal Articles by Gang Zhang
Papers by Gang Zhang