Trap characterization on GaN Schottky barrier diodes(SBDs)has been carried out using deep-level transient spectroscopy(DLTS).Selective probing by varying the ratio of the rate window values(r)incites different trap si...Trap characterization on GaN Schottky barrier diodes(SBDs)has been carried out using deep-level transient spectroscopy(DLTS).Selective probing by varying the ratio of the rate window values(r)incites different trap signatures at similar temperature regimes.Electron traps are found to be within the values:0.05–1.2 eV from the conduction band edge whereas the hole traps 1.37–2.66 eV from the valence band edge on the SBDs.In the lower temperature regime,the deeper electron traps contribute to the capacitance transients with increasing r values,whereas at the higher temperatures>300 K,a slow variation of the trap levels(both electrons and holes)is observed when r is varied.These traps are found to be mainly contributed to dislocations,interfaces,and vacancies within the structure.展开更多
A study of Cl2/BCl3-based inductively coupled plasma （ICP） was conducted using thick photoresist mask for anisotropic etching of 50μm diameter holes in a GaAs wafer at a relatively high average etching rate for etc...A study of Cl2/BCl3-based inductively coupled plasma （ICP） was conducted using thick photoresist mask for anisotropic etching of 50μm diameter holes in a GaAs wafer at a relatively high average etching rate for etching depths of more than 150μm. Plasma etch characteristics with ICP process pressure and the percentage of BCI3 were studied in greater detail at a constant ICP coil/bias power. The measured peak-to-peak voltage as a function of pressure was used to estimate the minimum energy of the ions bombarding the substrate. The process pressure was found to have a substantial influence on the energy of heavy ions. Various ion species in plasma showed minimum energy variation from 1.85 eV to 7.5 eV in the pressure range of 20 mTorr to 50 mTorr. The effect of pressure and the percentage of BCl3 on the etching rate and surface smoothness of the bottom surface of the etched hole were studied for a fixed total flow rate. The etching rate was found to decrease with the percentage of BCl3, whereas the addition of BCl3 resulted in anisotropic holes with a smooth veil free bottom surface at a pressure of 30 mTorr and 42% BC13. In addition, variation of the etching yield with pressure and etching depth were also investigated.展开更多
The discovery of the superconductivity with remarkably high critical temperature （TC ～ 39 K） in the binary intermetallic MgB2 compound [1] has given rise to a considerable effort in the condensed matter community i...The discovery of the superconductivity with remarkably high critical temperature （TC ～ 39 K） in the binary intermetallic MgB2 compound [1] has given rise to a considerable effort in the condensed matter community in the last three years. Indeed, it promises a higher operating temperature than Nb3Ge with TC = 23 K and unlike the cuprates it shows a lower anisotropy, larger coherence length, higher transparency of the grain boundaries for current flow, which makes it a good candidate for applications.展开更多
SnSe thin films of thickness 180 nm have been deposited on glass substrates by reactive evaporation at an optimized substrate temperature of 523 ± 5 K and pressure of 10^（-5） mbar.The as-prepared SnSe thin film...SnSe thin films of thickness 180 nm have been deposited on glass substrates by reactive evaporation at an optimized substrate temperature of 523 ± 5 K and pressure of 10^（-5） mbar.The as-prepared SnSe thin films are characterized for their structural,optical and electrical properties by various experimental techniques.The p-type conductivity,near-optimum direct band gap,high absorption coefficient and good photosensitivity of the SnSe thin film indicate its suitability for photovoltaic applications.The optical constants,loss factor,quality factor and optical conductivity of the films are evaluated.The results of Hall and thermoelectric power measurements are correlated to determine the density of states,Fermi energy and effective mass of carriers and are obtained as 2.8×10^（17）cm^（-3）,0.03 eV and 0.05m_0 respectively.The high Seebeck coefficient ≈ 7863 μV/K,reasonably good power factor ≈7.2×10^（-4） W/（m·K^2） and thermoelectric figure of merit ≈1.2 observed at 42 K suggests that,on further work,the prepared SnSe thin films can also be considered as a possible candidate for cryogenic thermoelectric applications.展开更多
Polycrystalline thin films of silver antimony selenide have been deposited using a reactive evaporation technique onto an ultrasonically cleaned glass substrate at a vacuum of 10-5 torr. The preparative parameters, li...Polycrystalline thin films of silver antimony selenide have been deposited using a reactive evaporation technique onto an ultrasonically cleaned glass substrate at a vacuum of 10-5 torr. The preparative parameters, like substrate temperature and incident fluxes, have been properly controlled in order to get stoichiometric, good quality and reproducible thin film samples. The samples are characterized by XRD, SEM, AFM and a UV-vis-NIR spectrophotometer. The prepared sample is found to be polycrystalline in nature. From the XRD pattern, the average particle size and lattice constant are calculated. The dislocation density, strain and number of crystallites per unit area are evaluated using the average particle size. The dependence of the electrical conductivity on the temperature has also been studied and the prepared AgSbSe2 samples are semiconducting in nature. The AgSbSe2 thin films exhibited an indirect allowed optical transition with a band gap of 0.64 eV. The compound exhibits promising thermoelectric properties, a large Seebeck coefficient of 30 mV/K at 48 K due to strong phonon electron interaction. It shows a strong temperature dependence on thermoelectric properties, including the inversion of a dominant carrier type from p to n over a low temperature range 9-300 K, which is explained on the basis of a phonon drag effect.展开更多
Graphene nanostructures are promising candidates for future nanoelectronics and solid-state quan- tum information technology. In this review we provide an overview of a number of electron transport experiments on etch...Graphene nanostructures are promising candidates for future nanoelectronics and solid-state quan- tum information technology. In this review we provide an overview of a number of electron transport experiments on etched graphene nanostructures. We briefly revisit the electronic properties and the transport characteristics of bulk, i.e., two-dimensional graphene. The fabrication techniques for making graphene nanostructures such as nanoribbons, single electron transistors and quantum dots, mainly based on a dry etching ＂paper-cutting＂ technique are discussed in detail. The limitations of the current fabrication technology are discussed when we outline the quantum transport properties of the nanostructured devices. In particular we focus here on transport through graphene nanoribbons and constrictions, single electron transistors as well as on graphene quantum dots including dou- ble quantum dots. These quasi-one-dimensional （nanoribbons） and quasi-zero-dimensional （quantum dots） graphene nanostructures show a clear route of how to overcome the gapless nature of graphene allowing the confinement of individual carriers and their control by lateral graphene gates and charge detectors. In particular, wo emphasize that graphene quantum dots and double quantum dots are very promising systems for spin-based solid state quantum computation, since they are believed to have exceptionally long spin coherence times due to weak spin-orbit coupling and weak hyperflne interaction in graphene.展开更多
This paper presents a development of a low-cost miniature humidity sensor with an interdigitated aluminium electrode connected in parallel on quartz substrate.Interdigitated capacitive device has been fabricated using...This paper presents a development of a low-cost miniature humidity sensor with an interdigitated aluminium electrode connected in parallel on quartz substrate.Interdigitated capacitive device has been fabricated using the photolithography method.The aluminium electrode was covered with sensitive film of a nanoporous thin film of γ-Al_(2)O_(3) made from novel solgel technique.Nanostructured thin film offers very high surface to volume ratio with distribution of micro pores for moisture detection.Pore morphologies of the film have been studied by field emission electron microscope and Xray diffraction methods.Impedance measurement of the miniature capacitive humidity sensor toward relative humidity was investigated at room temperature by Agilent 4294A impedance analyzer(Agilent,Santa Clara,CA,USA).The device exhibits short response and recovery times and good repeatability.展开更多
基金the financial support received from the Department of Science and Technology,India through DST-INSPIRE Faculty scheme(DST/INSPIRE/04/2015/001572).
文摘Trap characterization on GaN Schottky barrier diodes(SBDs)has been carried out using deep-level transient spectroscopy(DLTS).Selective probing by varying the ratio of the rate window values(r)incites different trap signatures at similar temperature regimes.Electron traps are found to be within the values:0.05–1.2 eV from the conduction band edge whereas the hole traps 1.37–2.66 eV from the valence band edge on the SBDs.In the lower temperature regime,the deeper electron traps contribute to the capacitance transients with increasing r values,whereas at the higher temperatures>300 K,a slow variation of the trap levels(both electrons and holes)is observed when r is varied.These traps are found to be mainly contributed to dislocations,interfaces,and vacancies within the structure.
文摘A study of Cl2/BCl3-based inductively coupled plasma （ICP） was conducted using thick photoresist mask for anisotropic etching of 50μm diameter holes in a GaAs wafer at a relatively high average etching rate for etching depths of more than 150μm. Plasma etch characteristics with ICP process pressure and the percentage of BCI3 were studied in greater detail at a constant ICP coil/bias power. The measured peak-to-peak voltage as a function of pressure was used to estimate the minimum energy of the ions bombarding the substrate. The process pressure was found to have a substantial influence on the energy of heavy ions. Various ion species in plasma showed minimum energy variation from 1.85 eV to 7.5 eV in the pressure range of 20 mTorr to 50 mTorr. The effect of pressure and the percentage of BCl3 on the etching rate and surface smoothness of the bottom surface of the etched hole were studied for a fixed total flow rate. The etching rate was found to decrease with the percentage of BCl3, whereas the addition of BCl3 resulted in anisotropic holes with a smooth veil free bottom surface at a pressure of 30 mTorr and 42% BC13. In addition, variation of the etching yield with pressure and etching depth were also investigated.
文摘The discovery of the superconductivity with remarkably high critical temperature （TC ～ 39 K） in the binary intermetallic MgB2 compound [1] has given rise to a considerable effort in the condensed matter community in the last three years. Indeed, it promises a higher operating temperature than Nb3Ge with TC = 23 K and unlike the cuprates it shows a lower anisotropy, larger coherence length, higher transparency of the grain boundaries for current flow, which makes it a good candidate for applications.
基金University Grants Commission (UGC), Government of India for financial assistance in the form of Research Fellowship in Science for Meritorious Students (RFSMS)
文摘SnSe thin films of thickness 180 nm have been deposited on glass substrates by reactive evaporation at an optimized substrate temperature of 523 ± 5 K and pressure of 10^（-5） mbar.The as-prepared SnSe thin films are characterized for their structural,optical and electrical properties by various experimental techniques.The p-type conductivity,near-optimum direct band gap,high absorption coefficient and good photosensitivity of the SnSe thin film indicate its suitability for photovoltaic applications.The optical constants,loss factor,quality factor and optical conductivity of the films are evaluated.The results of Hall and thermoelectric power measurements are correlated to determine the density of states,Fermi energy and effective mass of carriers and are obtained as 2.8×10^（17）cm^（-3）,0.03 eV and 0.05m_0 respectively.The high Seebeck coefficient ≈ 7863 μV/K,reasonably good power factor ≈7.2×10^（-4） W/（m·K^2） and thermoelectric figure of merit ≈1.2 observed at 42 K suggests that,on further work,the prepared SnSe thin films can also be considered as a possible candidate for cryogenic thermoelectric applications.
基金This work was supported by the Italian Ministry of Research （Ministero dell＇Istruzione, dell＇Universitae della Ricerca （MIUR）-Fondo per gli Investimenti della Ricerca di Base （FIRB） project No. RBID08B3FM） and by the Italian Ministry of Foreign Affairs （Ministero degli Affari Esteri, Direzione Generale per la Promozione del Sistema Paese, progetto： Nanoelettronica quantistica per le tecnologie delle informazioni）. Two of us （C.R. and W.W.） thank the Swiss National Science Foundation （SNSF） financial support.
文摘出现在传导力 G 0.7 睯物 ? 的异常运输特征的起源 ???????????? 瀠潲慰慧楴湯景 ? 慮潮楷敲？？
基金the University Grants Commission for the financial assistance in the form of a Research Fellowship in Science for Meritorious Students (RFSMS)
文摘Polycrystalline thin films of silver antimony selenide have been deposited using a reactive evaporation technique onto an ultrasonically cleaned glass substrate at a vacuum of 10-5 torr. The preparative parameters, like substrate temperature and incident fluxes, have been properly controlled in order to get stoichiometric, good quality and reproducible thin film samples. The samples are characterized by XRD, SEM, AFM and a UV-vis-NIR spectrophotometer. The prepared sample is found to be polycrystalline in nature. From the XRD pattern, the average particle size and lattice constant are calculated. The dislocation density, strain and number of crystallites per unit area are evaluated using the average particle size. The dependence of the electrical conductivity on the temperature has also been studied and the prepared AgSbSe2 samples are semiconducting in nature. The AgSbSe2 thin films exhibited an indirect allowed optical transition with a band gap of 0.64 eV. The compound exhibits promising thermoelectric properties, a large Seebeck coefficient of 30 mV/K at 48 K due to strong phonon electron interaction. It shows a strong temperature dependence on thermoelectric properties, including the inversion of a dominant carrier type from p to n over a low temperature range 9-300 K, which is explained on the basis of a phonon drag effect.
文摘Graphene nanostructures are promising candidates for future nanoelectronics and solid-state quan- tum information technology. In this review we provide an overview of a number of electron transport experiments on etched graphene nanostructures. We briefly revisit the electronic properties and the transport characteristics of bulk, i.e., two-dimensional graphene. The fabrication techniques for making graphene nanostructures such as nanoribbons, single electron transistors and quantum dots, mainly based on a dry etching ＂paper-cutting＂ technique are discussed in detail. The limitations of the current fabrication technology are discussed when we outline the quantum transport properties of the nanostructured devices. In particular we focus here on transport through graphene nanoribbons and constrictions, single electron transistors as well as on graphene quantum dots including dou- ble quantum dots. These quasi-one-dimensional （nanoribbons） and quasi-zero-dimensional （quantum dots） graphene nanostructures show a clear route of how to overcome the gapless nature of graphene allowing the confinement of individual carriers and their control by lateral graphene gates and charge detectors. In particular, wo emphasize that graphene quantum dots and double quantum dots are very promising systems for spin-based solid state quantum computation, since they are believed to have exceptionally long spin coherence times due to weak spin-orbit coupling and weak hyperflne interaction in graphene.
文摘This paper presents a development of a low-cost miniature humidity sensor with an interdigitated aluminium electrode connected in parallel on quartz substrate.Interdigitated capacitive device has been fabricated using the photolithography method.The aluminium electrode was covered with sensitive film of a nanoporous thin film of γ-Al_(2)O_(3) made from novel solgel technique.Nanostructured thin film offers very high surface to volume ratio with distribution of micro pores for moisture detection.Pore morphologies of the film have been studied by field emission electron microscope and Xray diffraction methods.Impedance measurement of the miniature capacitive humidity sensor toward relative humidity was investigated at room temperature by Agilent 4294A impedance analyzer(Agilent,Santa Clara,CA,USA).The device exhibits short response and recovery times and good repeatability.
