Thin films comprising nitrogen-doped ultrananocrystalline diamond/hydrogenated amorphous-carbon(UNCD/a-C:H)composite films were experimentally investigated.The prepared films were grown on Si substrates by the coaxial...Thin films comprising nitrogen-doped ultrananocrystalline diamond/hydrogenated amorphous-carbon(UNCD/a-C:H)composite films were experimentally investigated.The prepared films were grown on Si substrates by the coaxial arc plasma deposition method.They were characterized by temperature-dependent capacitance-frequency measurements in the temperature and frequency ranges of 300-400 K and 50 kHz-2 MHz,respectively.The energy distribution of trap density of states in the films was extracted using a simple technique utilizing the measured capacitance-frequency characteristics.In the measured temperature range,the energy-distributed traps exhibited Gaussian-distributed states with peak values lie in the range:2.84×10^(16)-2.73×10^(17)eV^(-1)cm^(-3)and centered at energies of 120-233 meV below the conduction band.These states are generated due to a large amount of sp^(2)-C andπ-bond states,localized in GBs of the UNCD/a-C:H film.The attained defect parameters are accommodating to understand basic electrical properties of UNCD/a-C:H composite and can be adopted to suppress defects in the UNCD-based materials.展开更多
An approximate formula is proposed for the decay rate of energy eigenfunctions in classically energetically inaccessible regions in more than one-dimensional configuration spaces. This is achieved by generalizing an a...An approximate formula is proposed for the decay rate of energy eigenfunctions in classically energetically inaccessible regions in more than one-dimensional configuration spaces. This is achieved by generalizing an approach proposed recently for energy eigenfunctions in the one-dimensional configuration space. The formula is tested numerically in the Pullen-Edmonds model.展开更多
It is shown that the traditional explanation of the free electron properties, such as mean free electron path, drift mobility, and the relaxation time, by lattice vibrations, is not valid for real free randomly moving...It is shown that the traditional explanation of the free electron properties, such as mean free electron path, drift mobility, and the relaxation time, by lattice vibrations, is not valid for real free randomly moving (RM) electrons in materials with degenerate electron gas. It is shown that the effective density of the free RM electrons in elemental metals is completely determined by density-of-states at the Fermi surface and by absolute temperature. The study has shown that the lattice vibrations excite not only the free RM electrons but also produce the same number of weakly screened ions (so-named electronic defects), which cause the scattering of the free RM electrons and related electron kinetic characteristics.展开更多
Thermoelectric materials possess the unique capability to convert thermal energy into electric energy and vice versa,making them promising for waste heat recovery and efficient cooling systems.Currently,extensively in...Thermoelectric materials possess the unique capability to convert thermal energy into electric energy and vice versa,making them promising for waste heat recovery and efficient cooling systems.Currently,extensively investigated thermoelectric materials such as Bi2Te3,PbTe and GeTe exhibit superior thermoelectric properties at room temperature and medium temperature regions.However,the broad application of these thermoelectric materials has been impeded by the high cost and restricted accessibility of Te and Ge in the earth's crust.Over the past few years,researchers have shown increasing interest in PbSe-and PbS-based materials,primarily attributed to their abundant elemental supply and relatively low costs.The assessment of research progress and a comprehensive overview of optimization strategies in time can significantly contribute to further improving the thermoelectric performance.These strategies include optimizing carrier concentration(aliovalent doping,dynamic doping and defect state),enhancing density-of-state effective mass(band convergence,band flattening and energy filtering effect),optimizing carrier mobility(band sharpening and band alignment)and reducing lattice thermal conductivity(all-scale hierarchical defect structures designing).This systematic summary and analysis provide novel insights and perspectives for the development of thermoelectric materials.展开更多
文摘Thin films comprising nitrogen-doped ultrananocrystalline diamond/hydrogenated amorphous-carbon(UNCD/a-C:H)composite films were experimentally investigated.The prepared films were grown on Si substrates by the coaxial arc plasma deposition method.They were characterized by temperature-dependent capacitance-frequency measurements in the temperature and frequency ranges of 300-400 K and 50 kHz-2 MHz,respectively.The energy distribution of trap density of states in the films was extracted using a simple technique utilizing the measured capacitance-frequency characteristics.In the measured temperature range,the energy-distributed traps exhibited Gaussian-distributed states with peak values lie in the range:2.84×10^(16)-2.73×10^(17)eV^(-1)cm^(-3)and centered at energies of 120-233 meV below the conduction band.These states are generated due to a large amount of sp^(2)-C andπ-bond states,localized in GBs of the UNCD/a-C:H film.The attained defect parameters are accommodating to understand basic electrical properties of UNCD/a-C:H composite and can be adopted to suppress defects in the UNCD-based materials.
基金Supported by the National Natural Science Foundation of China under Grant No 10275011.
文摘An approximate formula is proposed for the decay rate of energy eigenfunctions in classically energetically inaccessible regions in more than one-dimensional configuration spaces. This is achieved by generalizing an approach proposed recently for energy eigenfunctions in the one-dimensional configuration space. The formula is tested numerically in the Pullen-Edmonds model.
文摘It is shown that the traditional explanation of the free electron properties, such as mean free electron path, drift mobility, and the relaxation time, by lattice vibrations, is not valid for real free randomly moving (RM) electrons in materials with degenerate electron gas. It is shown that the effective density of the free RM electrons in elemental metals is completely determined by density-of-states at the Fermi surface and by absolute temperature. The study has shown that the lattice vibrations excite not only the free RM electrons but also produce the same number of weakly screened ions (so-named electronic defects), which cause the scattering of the free RM electrons and related electron kinetic characteristics.
基金supported by the Doctoral Research Startup Funding of Shijiazhuang University(No.22BS006)the National Natural Science Foundation of China(No.52102234)+1 种基金Hebei Province Introduced Overseas Talents Funding Project(No.C20210313)the College Students Innovation and Entrepreneurship Training Program of Shijiazhuang University(No.scxm063)。
文摘Thermoelectric materials possess the unique capability to convert thermal energy into electric energy and vice versa,making them promising for waste heat recovery and efficient cooling systems.Currently,extensively investigated thermoelectric materials such as Bi2Te3,PbTe and GeTe exhibit superior thermoelectric properties at room temperature and medium temperature regions.However,the broad application of these thermoelectric materials has been impeded by the high cost and restricted accessibility of Te and Ge in the earth's crust.Over the past few years,researchers have shown increasing interest in PbSe-and PbS-based materials,primarily attributed to their abundant elemental supply and relatively low costs.The assessment of research progress and a comprehensive overview of optimization strategies in time can significantly contribute to further improving the thermoelectric performance.These strategies include optimizing carrier concentration(aliovalent doping,dynamic doping and defect state),enhancing density-of-state effective mass(band convergence,band flattening and energy filtering effect),optimizing carrier mobility(band sharpening and band alignment)and reducing lattice thermal conductivity(all-scale hierarchical defect structures designing).This systematic summary and analysis provide novel insights and perspectives for the development of thermoelectric materials.
