Niobium is sputtered onto a single crystalline silicon substrate in N2：Ar=4：1 gas mixture at the total pressure of 2 Pa. The temperature coefficient of resistance of the sample is about 0.5% at 30OK, and up to 7% at...Niobium is sputtered onto a single crystalline silicon substrate in N2：Ar=4：1 gas mixture at the total pressure of 2 Pa. The temperature coefficient of resistance of the sample is about 0.5% at 30OK, and up to 7% at 77K, indicating the possibility of using it to make room-temperature bolometers with performances better than those based on Pt, Bi, or Nb. For a 60-nm-thick sample, the rms surface roughness is 0.45nm over an area of 2 μm × 2 μm. Analyses based on x-ray diffraction and x-ray photoelectronic spectroscopy indicate that the samples are Nb5N6 thin films in which there is a combination of Nb^3＋ and Nb^5＋, or Nb^4＋.展开更多
A novel room-temperature microbolometer array chip consisting of an Nb5N6 thin film microbridge and a dipole planar antenna, which is used as a terahertz （THz） detector, is described in this paper. Due to the high-t...A novel room-temperature microbolometer array chip consisting of an Nb5N6 thin film microbridge and a dipole planar antenna, which is used as a terahertz （THz） detector, is described in this paper. Due to the high-temperature coefficient of the resistance of the Nb5N6 thin film, which is as high as –0.7% K-1 , such an antenna-coupled microbolometer is ideal for detecting signals in a frequency range from 0.22THz to 0.33THz. The dc responsivity, calculated from the measured I–V curve of the Nb5N6 microbolometer, is about –760 V/W at a bias current of 0.19mA. A typical noise voltage as low as 10 nV/Hz 1/2 yields a low noise equivalent power （NEP） of 1.3×10-11W/Hz 1/2 at a modulation frequency above 4kHz, and the best RF responsivity, characterized using an infrared device measuring method, is about 580V/W, with the corresponding NEP being 1.7×10-11W/Hz 1/2 . In order to further test the performance of the Nb5N6 microbolometer, we construct a quasi-optical type receiver by attaching it to a hyperhemispherical silicon lens, and the result is that the best responsivity of the receiver is up to 320V/W. This work could offer another way to develop a large scale focal-plane array in silicon using simple techniques and at low cost.展开更多
A simple technique is reported for fabricating the mesa structure on Bi2Sr2CaCu2O8+δ single crystal. In the patterning process, metal masks are used instead of photolithography and argon ion milling is applied to for...A simple technique is reported for fabricating the mesa structure on Bi2Sr2CaCu2O8+δ single crystal. In the patterning process, metal masks are used instead of photolithography and argon ion milling is applied to form the small mesa on the Bi2Sr2CaCu2O8+δ crystal surface. Real four-probe transport measurements are made on the mesa structure and typical c-axis current-voltage (I - V) characteristics of the intrinsic Josephson effect have been observed. The superconducting gap parameter can be extracted from the multi-branch structure in the I - V characteristics. Additionally, from the strong hysteresis in the I - V characteristics, the capacitance CJ of the unit intrinsic Josephson junction has been estimated to be 2.3pF, which is in good agreement with that evaluated from the geometric parameters of the unit junction between the two copper oxide layers.展开更多
Microstructural change of YBaCuO film/YSZ substrate with and without proton irradiation has been studied by scanning electron microscope and X- ray diffraction techniques. Structural analysis has shown that conversion...Microstructural change of YBaCuO film/YSZ substrate with and without proton irradiation has been studied by scanning electron microscope and X- ray diffraction techniques. Structural analysis has shown that conversion from tetragonal to orthorhombic phases, reduction of nonsuperconducting phase and preferential rearrangement of crystal grains are all favorable to the improvement of superconductivity in the YBaCuO film supported by YSZ substrate by proton beam bombardment.展开更多
The critical current density behaviors across a bicrystal grain boundary（GB） inclined to the current direction with different angles in YBa2Cu3O7-δ bicrystal junctions in magnetic fields are investigated.There are...The critical current density behaviors across a bicrystal grain boundary（GB） inclined to the current direction with different angles in YBa2Cu3O7-δ bicrystal junctions in magnetic fields are investigated.There are two main reasons for the difference in critical current density in junctions at different GB inclined angles in the same magnetic field：（i） the GB plane area determines the current carrying cross section;（ii） the vortex motion dynamics at the GB affects the critical current value when the vortex starts to move along the GB by Lorentz force.Furthermore,the vortex motion in a bicrystal GB is studied by investigating transverse（Hall） and longitudinal current–voltage characteristics（I–Vxx and I–Vxy）.It is found that the I–Vxx curve diverges from linearity at a high driving current,while the I–Vxy curve keeps nearly linear,which indicates the vortices inside the GB break out of the GB by Lorentz force.展开更多
Pb-doped HgBa_(2)CaCu_(2)O_(y) films were prepared on the(100)SrTiO_(3) substrate by using laser ablation followed by post-Hg-vapor annealing.These films are dominated by c-axis-oriented Hg-1212 phase as indicated by ...Pb-doped HgBa_(2)CaCu_(2)O_(y) films were prepared on the(100)SrTiO_(3) substrate by using laser ablation followed by post-Hg-vapor annealing.These films are dominated by c-axis-oriented Hg-1212 phase as indicated by x-ray diffraction and electromagnetic measurements.The transition temperature Tc0 is 110 K.The critical current density Jc achieved 10^(6) A/cm^(2) at 77K and zero applied field.展开更多
文摘Niobium is sputtered onto a single crystalline silicon substrate in N2：Ar=4：1 gas mixture at the total pressure of 2 Pa. The temperature coefficient of resistance of the sample is about 0.5% at 30OK, and up to 7% at 77K, indicating the possibility of using it to make room-temperature bolometers with performances better than those based on Pt, Bi, or Nb. For a 60-nm-thick sample, the rms surface roughness is 0.45nm over an area of 2 μm × 2 μm. Analyses based on x-ray diffraction and x-ray photoelectronic spectroscopy indicate that the samples are Nb5N6 thin films in which there is a combination of Nb^3＋ and Nb^5＋, or Nb^4＋.
基金Project supported by the National Basic Research Program of China (Grant No. 2011CBA00107)the National High-Technology Research Development Program of China (Grant No. 2011AA010204)
文摘A novel room-temperature microbolometer array chip consisting of an Nb5N6 thin film microbridge and a dipole planar antenna, which is used as a terahertz （THz） detector, is described in this paper. Due to the high-temperature coefficient of the resistance of the Nb5N6 thin film, which is as high as –0.7% K-1 , such an antenna-coupled microbolometer is ideal for detecting signals in a frequency range from 0.22THz to 0.33THz. The dc responsivity, calculated from the measured I–V curve of the Nb5N6 microbolometer, is about –760 V/W at a bias current of 0.19mA. A typical noise voltage as low as 10 nV/Hz 1/2 yields a low noise equivalent power （NEP） of 1.3×10-11W/Hz 1/2 at a modulation frequency above 4kHz, and the best RF responsivity, characterized using an infrared device measuring method, is about 580V/W, with the corresponding NEP being 1.7×10-11W/Hz 1/2 . In order to further test the performance of the Nb5N6 microbolometer, we construct a quasi-optical type receiver by attaching it to a hyperhemispherical silicon lens, and the result is that the best responsivity of the receiver is up to 320V/W. This work could offer another way to develop a large scale focal-plane array in silicon using simple techniques and at low cost.
基金the National Center for Research and Development on Superconductivity of Chinain part by the International Collaborative Research Project of Telecommunications Advancement Organization of Japan.
文摘A simple technique is reported for fabricating the mesa structure on Bi2Sr2CaCu2O8+δ single crystal. In the patterning process, metal masks are used instead of photolithography and argon ion milling is applied to form the small mesa on the Bi2Sr2CaCu2O8+δ crystal surface. Real four-probe transport measurements are made on the mesa structure and typical c-axis current-voltage (I - V) characteristics of the intrinsic Josephson effect have been observed. The superconducting gap parameter can be extracted from the multi-branch structure in the I - V characteristics. Additionally, from the strong hysteresis in the I - V characteristics, the capacitance CJ of the unit intrinsic Josephson junction has been estimated to be 2.3pF, which is in good agreement with that evaluated from the geometric parameters of the unit junction between the two copper oxide layers.
文摘Microstructural change of YBaCuO film/YSZ substrate with and without proton irradiation has been studied by scanning electron microscope and X- ray diffraction techniques. Structural analysis has shown that conversion from tetragonal to orthorhombic phases, reduction of nonsuperconducting phase and preferential rearrangement of crystal grains are all favorable to the improvement of superconductivity in the YBaCuO film supported by YSZ substrate by proton beam bombardment.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61501222,61371036,and 61571219)the School Scientific Research Fund of Nanjing Institute of Technology,China(Grant Nos.YKJ201418)
文摘The critical current density behaviors across a bicrystal grain boundary（GB） inclined to the current direction with different angles in YBa2Cu3O7-δ bicrystal junctions in magnetic fields are investigated.There are two main reasons for the difference in critical current density in junctions at different GB inclined angles in the same magnetic field：（i） the GB plane area determines the current carrying cross section;（ii） the vortex motion dynamics at the GB affects the critical current value when the vortex starts to move along the GB by Lorentz force.Furthermore,the vortex motion in a bicrystal GB is studied by investigating transverse（Hall） and longitudinal current–voltage characteristics（I–Vxx and I–Vxy）.It is found that the I–Vxx curve diverges from linearity at a high driving current,while the I–Vxy curve keeps nearly linear,which indicates the vortices inside the GB break out of the GB by Lorentz force.
基金Supported by the National Center for Research and Development on Superconductivity of Chinathe Foundation for Doctoral Education.
文摘Pb-doped HgBa_(2)CaCu_(2)O_(y) films were prepared on the(100)SrTiO_(3) substrate by using laser ablation followed by post-Hg-vapor annealing.These films are dominated by c-axis-oriented Hg-1212 phase as indicated by x-ray diffraction and electromagnetic measurements.The transition temperature Tc0 is 110 K.The critical current density Jc achieved 10^(6) A/cm^(2) at 77K and zero applied field.
