Vanadium dioxide （VO2） is a phase transition material which undergoes a reversible metal-insulator transition （MIT） when triggered by thermal, photo, electrical, and even stress. The huge conduction change of VO2 ...Vanadium dioxide （VO2） is a phase transition material which undergoes a reversible metal-insulator transition （MIT） when triggered by thermal, photo, electrical, and even stress. The huge conduction change of VO2 renders it a promising material for terahertz （THz） manipulation. In this paper, some interesting works concerning the growth and characteristics of the VO2 film are selectively reviewed. A switching of THz radiation by photo-driven VO2 film is demonstrated. Experiments indicate an ultrafast optical switching to THz transmission within 8 picoseconds, and a switching ratio reaches to over 80%during a wide frequency range from 0.3 THz to 2.5 THz.展开更多
The superconducting quantum interference device（SQUID） amplifier is widely used in the field of weak signal detection for its low input impedance, low noise, and low power consumption. In this paper, the SQUIDs with...The superconducting quantum interference device（SQUID） amplifier is widely used in the field of weak signal detection for its low input impedance, low noise, and low power consumption. In this paper, the SQUIDs with identical junctions and the series SQUIDs with different junctions were successfully fabricated. The Nb/Al-AlOx/Nb trilayer and input Nb coils were prepared by asputtering equipment. The SQUID devices were prepared by a sputtering and the lift-off method.Investigations by AFM, OM and SEM revealed the morphology and roughness of the Nb films and Nb/Al-AlOx/Nb trilayer.In addition, the current–voltage characteristics of the SQUID devices with identical junction and different junction areas were measured at 2.5 K in the He^3 refrigerator. The results show that the SQUID modulation depth is obviously affected by the junction area. The modulation depth obviously increases with the increase of the junction area in a certain range. It is found that the series SQUID with identical junction area has a transimpedance gain of 58 Ω approximately.展开更多
In the past few years, two-dimensional （2D） transition metal dichalcogenide （TMDC） materials have attracted increasing attention of the research community, owing to their unique electronic and optical properties, ...In the past few years, two-dimensional （2D） transition metal dichalcogenide （TMDC） materials have attracted increasing attention of the research community, owing to their unique electronic and optical properties, ranging from the valley-spin coupling to the indirect-to-direct bandgap transition when scaling the materials from multi-layer to monolayer. These properties are appealing for the development of novel electronic and optoelectronic devices with important applications in the broad fields of communication, computation, and healthcare. One of the key features of the TMDC family is the indirect-to-direct bandgap transition that occurs when the material thickness decreases from multilayer to monolayer, which is favorable for many photonic applications. TMDCs have also demonstrated unprecedented flexibility and versatility for constructing a wide range of heterostructures with atomic-level control over their layer thickness that is also free of lattice mismatch issues. As a result, layered TMDCs in combination with other 2D materials have the potential for realizing novel high-performance optoelectronic devices over a broad operating spectral range. In this article, we review the recent progress in the synthesis of 2D TMDCs and optoelectronic devices research. We also discuss the challenges facing the scalable applications of the family of 2D materials and provide our perspective on the opportunities offered by these materials for future generations of nanophotonics technology.展开更多
A new model is developed to study the microwave/mm wave characteristics of two-terminal GaNbased transfer electron devices（TEDs）,namely a Gunn diode and an impact avalanche transit time（IMPATT） device.Microwave ch...A new model is developed to study the microwave/mm wave characteristics of two-terminal GaNbased transfer electron devices（TEDs）,namely a Gunn diode and an impact avalanche transit time（IMPATT） device.Microwave characteristics such as device efficiency and the microwave power generated are computed and compared at D-band（140 GHz center frequency） to see the potentiality of each device under the same operating conditions.It is seen that GaN-based IMPATT devices surpass the Gunn diode in the said frequency region.展开更多
基金supported by the National Natural Science Foundation of China under Grant No.61131005Keygrant Project of Chinese Ministry of Education under Grant No.313013+1 种基金New Century Excellent Talent Foundation under Grant No.NCET-11-0068Sichuan Youth S.&T.Foundation under Grant No.2011JQ0001
文摘Vanadium dioxide （VO2） is a phase transition material which undergoes a reversible metal-insulator transition （MIT） when triggered by thermal, photo, electrical, and even stress. The huge conduction change of VO2 renders it a promising material for terahertz （THz） manipulation. In this paper, some interesting works concerning the growth and characteristics of the VO2 film are selectively reviewed. A switching of THz radiation by photo-driven VO2 film is demonstrated. Experiments indicate an ultrafast optical switching to THz transmission within 8 picoseconds, and a switching ratio reaches to over 80%during a wide frequency range from 0.3 THz to 2.5 THz.
基金Project supported by the National Natural Science Foundation of China(Grant No.11653001)the National Basic Research Program of China(Grant No.2011CBA00304)Tsinghua University Initiative Scientific Research Program,China(Grant No.20131089314)
文摘The superconducting quantum interference device（SQUID） amplifier is widely used in the field of weak signal detection for its low input impedance, low noise, and low power consumption. In this paper, the SQUIDs with identical junctions and the series SQUIDs with different junctions were successfully fabricated. The Nb/Al-AlOx/Nb trilayer and input Nb coils were prepared by asputtering equipment. The SQUID devices were prepared by a sputtering and the lift-off method.Investigations by AFM, OM and SEM revealed the morphology and roughness of the Nb films and Nb/Al-AlOx/Nb trilayer.In addition, the current–voltage characteristics of the SQUID devices with identical junction and different junction areas were measured at 2.5 K in the He^3 refrigerator. The results show that the SQUID modulation depth is obviously affected by the junction area. The modulation depth obviously increases with the increase of the junction area in a certain range. It is found that the series SQUID with identical junction area has a transimpedance gain of 58 Ω approximately.
文摘In the past few years, two-dimensional （2D） transition metal dichalcogenide （TMDC） materials have attracted increasing attention of the research community, owing to their unique electronic and optical properties, ranging from the valley-spin coupling to the indirect-to-direct bandgap transition when scaling the materials from multi-layer to monolayer. These properties are appealing for the development of novel electronic and optoelectronic devices with important applications in the broad fields of communication, computation, and healthcare. One of the key features of the TMDC family is the indirect-to-direct bandgap transition that occurs when the material thickness decreases from multilayer to monolayer, which is favorable for many photonic applications. TMDCs have also demonstrated unprecedented flexibility and versatility for constructing a wide range of heterostructures with atomic-level control over their layer thickness that is also free of lattice mismatch issues. As a result, layered TMDCs in combination with other 2D materials have the potential for realizing novel high-performance optoelectronic devices over a broad operating spectral range. In this article, we review the recent progress in the synthesis of 2D TMDCs and optoelectronic devices research. We also discuss the challenges facing the scalable applications of the family of 2D materials and provide our perspective on the opportunities offered by these materials for future generations of nanophotonics technology.
基金Project supported by the Department of Science and TechnologyGovernment of India through SERC,FIST and TIFAC Program
文摘A new model is developed to study the microwave/mm wave characteristics of two-terminal GaNbased transfer electron devices（TEDs）,namely a Gunn diode and an impact avalanche transit time（IMPATT） device.Microwave characteristics such as device efficiency and the microwave power generated are computed and compared at D-band（140 GHz center frequency） to see the potentiality of each device under the same operating conditions.It is seen that GaN-based IMPATT devices surpass the Gunn diode in the said frequency region.
