Efficient and stable bifunctional electrocatalysts for water splitting is essential for producing hydrogen and alleviating huge energy consumption.Meanwhile,charge transfer engineering is an efficient approach to modu...Efficient and stable bifunctional electrocatalysts for water splitting is essential for producing hydrogen and alleviating huge energy consumption.Meanwhile,charge transfer engineering is an efficient approach to modulate the localized electronic properties of catalysts and tune the electrocatalytic performance.Herein,we tactfully fabricate PtFeNi alloys/NiFe layered double hydroxides(LDHs)heterostructure by an easily electrochemical way with a small amount of Pt.The experimental and theoretical results unravel that the charge transfer on the alloy clusters modulated by the defective substrates(NiFe LDHs),which synergistically optimizes the adsorption energy of the reaction intermediates.The electrocatalyst exhibits an ultra‐low overpotential of 81 and 243 mV at the current density of 100 mA cm^(–2) for hydrogen evolution and oxygen evolution,respectively.Furthermore,the overall water splitting indicates that PtFeNi alloys/NiFe LDHs presents an ultra‐low overpotential of 265 and 406 mV to reach the current density of 10 and 300 mA cm^(–2),respectively.It proves that the PtFeNi alloys/NiFe LDHs catalyst is an excellent dual‐function electrocatalyst for water splitting and promising for industrialization.This work provides a new electrochemical approach to construct the alloy heterostructure.The prepared heterostructures act as an ideal platform to investigate the charge re‐distribution behavior and to improve the electrocatalytic activity.展开更多
High-speed optical switch and its array are the crucial components of all-optical switching system.This paper presents the analytical model of a total-internal-reflection(TIR) optical switch.By employing the carrier i...High-speed optical switch and its array are the crucial components of all-optical switching system.This paper presents the analytical model of a total-internal-reflection(TIR) optical switch.By employing the carrier injection effect in GaAs and the GaAs/AlGaAs double heterojunction structure,the X-junction TIR switch and the Mach-Zehnder interference(MZI) switch are demonstrated at 1.55 μm.The measured results show that the extinction ratio of both switches exceeds 20 dB.The switching speed reaches the scale of 10 ns.展开更多
A non-micro-air-bridge InP-based heterojunction bipolar transistor （HBT） is fabricated. A very small emitter side etching （〈100nm） is developed and makes a submicron InP-based HBT possible. The current gain cutof...A non-micro-air-bridge InP-based heterojunction bipolar transistor （HBT） is fabricated. A very small emitter side etching （〈100nm） is developed and makes a submicron InP-based HBT possible. The current gain cutoff frequency is as high as 238GHz for the submicron HBT with an emitter area of 0.8μm × 15μm due to the reduction of emitter width. A base-collector over-etching technology is developed,resulting in a reduction of base-collector junction area and an increase in the maximum oscillation frequency. A very high Kirk current density of 3. 1mA/μm^2 is obtained. To the best of our knowledge,the current gain cutoff frequency is the highest among three-terminal devices in China and the Kirk current density is also the highest in HBTs reported in China. This is very helpful for the application of HBTs in ultra high-speed circuits.展开更多
We experimentally demonstrate an efficient enhancement of luminescence from two-dimensional(2D) hexagonal photonic crystal(PC) airbridge double-heterostructure microcavity with Er-doped silicon(Si) as light emitters o...We experimentally demonstrate an efficient enhancement of luminescence from two-dimensional(2D) hexagonal photonic crystal(PC) airbridge double-heterostructure microcavity with Er-doped silicon(Si) as light emitters on siliconon-insulator(SOI) wafer at room temperature.A single sharp resonant peak at 1 529.6 nm dominates the photoluminescence(PL) spectrum with the pumping power of 12.5 m W.The obvious red shift and the degraded quality factor(Q-factor) of resonant peak appear with the pumping power increasing,and the maximum measured Q-factor of 4 905 is achieved at the pumping power of 1.5 m W.The resonant peak is observed to shift depending on the structural parameters of PC,which indicates a possible method to control the wavelength of enhanced luminescence for Si-based light emitters based on PC microcavity.展开更多
文摘Efficient and stable bifunctional electrocatalysts for water splitting is essential for producing hydrogen and alleviating huge energy consumption.Meanwhile,charge transfer engineering is an efficient approach to modulate the localized electronic properties of catalysts and tune the electrocatalytic performance.Herein,we tactfully fabricate PtFeNi alloys/NiFe layered double hydroxides(LDHs)heterostructure by an easily electrochemical way with a small amount of Pt.The experimental and theoretical results unravel that the charge transfer on the alloy clusters modulated by the defective substrates(NiFe LDHs),which synergistically optimizes the adsorption energy of the reaction intermediates.The electrocatalyst exhibits an ultra‐low overpotential of 81 and 243 mV at the current density of 100 mA cm^(–2) for hydrogen evolution and oxygen evolution,respectively.Furthermore,the overall water splitting indicates that PtFeNi alloys/NiFe LDHs presents an ultra‐low overpotential of 265 and 406 mV to reach the current density of 10 and 300 mA cm^(–2),respectively.It proves that the PtFeNi alloys/NiFe LDHs catalyst is an excellent dual‐function electrocatalyst for water splitting and promising for industrialization.This work provides a new electrochemical approach to construct the alloy heterostructure.The prepared heterostructures act as an ideal platform to investigate the charge re‐distribution behavior and to improve the electrocatalytic activity.
基金Supported by the Key Fund of National Natural Science Foundation of China (Grant No. 60436020)
文摘High-speed optical switch and its array are the crucial components of all-optical switching system.This paper presents the analytical model of a total-internal-reflection(TIR) optical switch.By employing the carrier injection effect in GaAs and the GaAs/AlGaAs double heterojunction structure,the X-junction TIR switch and the Mach-Zehnder interference(MZI) switch are demonstrated at 1.55 μm.The measured results show that the extinction ratio of both switches exceeds 20 dB.The switching speed reaches the scale of 10 ns.
文摘A non-micro-air-bridge InP-based heterojunction bipolar transistor （HBT） is fabricated. A very small emitter side etching （〈100nm） is developed and makes a submicron InP-based HBT possible. The current gain cutoff frequency is as high as 238GHz for the submicron HBT with an emitter area of 0.8μm × 15μm due to the reduction of emitter width. A base-collector over-etching technology is developed,resulting in a reduction of base-collector junction area and an increase in the maximum oscillation frequency. A very high Kirk current density of 3. 1mA/μm^2 is obtained. To the best of our knowledge,the current gain cutoff frequency is the highest among three-terminal devices in China and the Kirk current density is also the highest in HBTs reported in China. This is very helpful for the application of HBTs in ultra high-speed circuits.
基金supported by the National Natural Science Foundation of China(No.61205044)
文摘We experimentally demonstrate an efficient enhancement of luminescence from two-dimensional(2D) hexagonal photonic crystal(PC) airbridge double-heterostructure microcavity with Er-doped silicon(Si) as light emitters on siliconon-insulator(SOI) wafer at room temperature.A single sharp resonant peak at 1 529.6 nm dominates the photoluminescence(PL) spectrum with the pumping power of 12.5 m W.The obvious red shift and the degraded quality factor(Q-factor) of resonant peak appear with the pumping power increasing,and the maximum measured Q-factor of 4 905 is achieved at the pumping power of 1.5 m W.The resonant peak is observed to shift depending on the structural parameters of PC,which indicates a possible method to control the wavelength of enhanced luminescence for Si-based light emitters based on PC microcavity.
