Electrical properties of high quality ultra thin nitride/oxynitride(N/O)stack dielectrics pMOS capacitor with refractory metal gate electrode are investigated,and ultra thin (<2 nm) N/O stack gate dielectrics with ...Electrical properties of high quality ultra thin nitride/oxynitride(N/O)stack dielectrics pMOS capacitor with refractory metal gate electrode are investigated,and ultra thin (<2 nm) N/O stack gate dielectrics with significant low leakage current and high resistance to boron penetration are fabricated.Experiment results show that the stack gate dielectric of nitride/oxynitride combined with improved sputtered tungsten/titanium nitride (W/TiN) gate electrode is one of the candidates for deep sub-micron metal gate CMOS devices.展开更多
Jiuzhaigou, characterized by its magnificent waterscapes and subalpine karstic features, is both a World Heritage Site and a World Biosphere Reserve in southwestern China. In recent years, this unique ecosystem has sh...Jiuzhaigou, characterized by its magnificent waterscapes and subalpine karstic features, is both a World Heritage Site and a World Biosphere Reserve in southwestern China. In recent years, this unique ecosystem has shown signs of stress due to increasing tourism activities within the reserve. The various routine methods, which monitor physical and chemical properties, do not fully reflect water quality in the subalpine and alpine lakes, while the indicators using aquatic organisms to evaluate the water quality or status of the subalpine lakes are poorly reported. Thus, in this study, benthic diatoms from multiple habitats in Jiuzhaigou were sampled and assessed for water quality monitoring. Canonical Correspondence Analysis （CCA） showed that the canonical coefficients for elevation, water temperature and total nitrogen on the first Canonical Corresnondence Analysis axis were -0.84. 0.78 and -0.53, respectively, environmental variables associated with the distribution patterns of benthic diatoms. The dominance of diatom taxa indicative of nutrient enrichment indicates a clear trend toward eutrophication in the Pearl Shoal and Colorful Lake, two of the sites mostly visited by tourists. It was observed that the effect of the type of substratum on diatom community composition is not significant in subalpine lakes. The most dominant species in Jiuzhaigou lakes are the genera Achnanthes, Fragilaria, CymbeUa, Cocconeis, Diatoma and Denticula. In combination with dominant and sensitive species in the benthic diatom communities, CCA and CA methods can be used to evaluate the impact of human activities on subalpine karstic lakes. The dominance of diatom taxa is indicative of nutrient enrichment and the results of CCA and CA indicate a clear trend toward eutrophication in the Pearl Shoal and Colorful Lake, two of the sites mostly visited by tourists.展开更多
To reveal the possible mechanism of silica deposition in higher plants, lignin was isolated from rice straw following a modified method to conduct a simulation experiment in vitro. UV and infrared absorption spectra s...To reveal the possible mechanism of silica deposition in higher plants, lignin was isolated from rice straw following a modified method to conduct a simulation experiment in vitro. UV and infrared absorption spectra showed that the substance had the unique characteristics of pure lignin. The presence of silicon in the precipitation was revealed by TEM (transmission electron microscopy) with EDXA (energy dispersive X-ray analysis) device. It was found that in the borax solution where lignin precipi-tation occurred silica-lignin co-precipitation was produced but not in the DMSO solution where lignin was broken into its com-position compounds and did not precipitate. This means that it is macromolecular lignin itself but not its compounds that could induce silica deposition in higher plants.展开更多
Metamorphic Al0.50In0.50As/Ga0.47In0.53As high electron mobility transistors (mHEMTs) grown by Metal Organic ChemicalVapor Deposition (MOCVD) on n-type silicon substrates with introduction of a novel multi-stage buffe...Metamorphic Al0.50In0.50As/Ga0.47In0.53As high electron mobility transistors (mHEMTs) grown by Metal Organic ChemicalVapor Deposition (MOCVD) on n-type silicon substrates with introduction of a novel multi-stage buffering stack scheme havebeen fabricated for the first time. 1.0- m-gate-length depletion-mode mHEMTs with maximum transconductance up to 613mS/mm are achieved. The unity current gain cut-off frequency (fT) and the maximum oscillation frequency (fmax) are 36.9 and55.6 GHz, respectively. This device has the highest fTyet reported for 1.0- m-gate-length HEMTs grown on silicon byMOCVD. Also, this performance is comparable to that of similar GaAs-based mHEMTs. These are encouraging initial resultsleading to the manufacturing potential of integrated high-speed metamorphic devices for logic applications on silicon sub-strates by MOCVD.展开更多
We present an InGaAs metamorphic high electron mobility transistor （mHEMT） grown using Metalorganic Chemical Vapor Deposition （MOCVD） on an n-type silicon substrate with the introduction of an effective multi-stag...We present an InGaAs metamorphic high electron mobility transistor （mHEMT） grown using Metalorganic Chemical Vapor Deposition （MOCVD） on an n-type silicon substrate with the introduction of an effective multi-stage buffering scheme. Fabrication and performance of a high-frequency 0.3μm gate-length depletion-mode A10.s0In0.s0As/Ga0.47In0.53As mHEMT is re- ported for the first time. Using a combined optical and e-beam photolithography technology, submicron mHEMT devices on Si have been achieved. The non-alloyed ohmic contact resistance Rc was as low as 0.065 Ω-mm. A maximum transconductance up to 761 mS/ram was measured. The unity current gain cut-off frequency （fT） and the maximum oscillation frequency （fmax） were 72.8 and 74.5 GHz, respectively. This device has the highest fw yet reported for a 0.3-μm gate-length Si-based mHEMT grown using MOCVD. A high voltage gain, gm/gds, of 40.6 is observed in the device.展开更多
文摘Electrical properties of high quality ultra thin nitride/oxynitride(N/O)stack dielectrics pMOS capacitor with refractory metal gate electrode are investigated,and ultra thin (<2 nm) N/O stack gate dielectrics with significant low leakage current and high resistance to boron penetration are fabricated.Experiment results show that the stack gate dielectric of nitride/oxynitride combined with improved sputtered tungsten/titanium nitride (W/TiN) gate electrode is one of the candidates for deep sub-micron metal gate CMOS devices.
基金funded by the Programme of Introducing Talents of Discipline to Universities(the 111 Project)(grant no.B08037)National Key Technology R&D Program of China(grant no.2012BAC06B02)
文摘Jiuzhaigou, characterized by its magnificent waterscapes and subalpine karstic features, is both a World Heritage Site and a World Biosphere Reserve in southwestern China. In recent years, this unique ecosystem has shown signs of stress due to increasing tourism activities within the reserve. The various routine methods, which monitor physical and chemical properties, do not fully reflect water quality in the subalpine and alpine lakes, while the indicators using aquatic organisms to evaluate the water quality or status of the subalpine lakes are poorly reported. Thus, in this study, benthic diatoms from multiple habitats in Jiuzhaigou were sampled and assessed for water quality monitoring. Canonical Correspondence Analysis （CCA） showed that the canonical coefficients for elevation, water temperature and total nitrogen on the first Canonical Corresnondence Analysis axis were -0.84. 0.78 and -0.53, respectively, environmental variables associated with the distribution patterns of benthic diatoms. The dominance of diatom taxa indicative of nutrient enrichment indicates a clear trend toward eutrophication in the Pearl Shoal and Colorful Lake, two of the sites mostly visited by tourists. It was observed that the effect of the type of substratum on diatom community composition is not significant in subalpine lakes. The most dominant species in Jiuzhaigou lakes are the genera Achnanthes, Fragilaria, CymbeUa, Cocconeis, Diatoma and Denticula. In combination with dominant and sensitive species in the benthic diatom communities, CCA and CA methods can be used to evaluate the impact of human activities on subalpine karstic lakes. The dominance of diatom taxa is indicative of nutrient enrichment and the results of CCA and CA indicate a clear trend toward eutrophication in the Pearl Shoal and Colorful Lake, two of the sites mostly visited by tourists.
基金Projects supported by the National Natural Science Foundation of China (No. 30170550), the Natural Science Foundation of Anhui Provincial Education Department (No. 2005kj398zc) and the Culture Project for "the Tenth Five-year" Learning Leaders of Higher School of Anhui Province, China
文摘To reveal the possible mechanism of silica deposition in higher plants, lignin was isolated from rice straw following a modified method to conduct a simulation experiment in vitro. UV and infrared absorption spectra showed that the substance had the unique characteristics of pure lignin. The presence of silicon in the precipitation was revealed by TEM (transmission electron microscopy) with EDXA (energy dispersive X-ray analysis) device. It was found that in the borax solution where lignin precipi-tation occurred silica-lignin co-precipitation was produced but not in the DMSO solution where lignin was broken into its com-position compounds and did not precipitate. This means that it is macromolecular lignin itself but not its compounds that could induce silica deposition in higher plants.
文摘Metamorphic Al0.50In0.50As/Ga0.47In0.53As high electron mobility transistors (mHEMTs) grown by Metal Organic ChemicalVapor Deposition (MOCVD) on n-type silicon substrates with introduction of a novel multi-stage buffering stack scheme havebeen fabricated for the first time. 1.0- m-gate-length depletion-mode mHEMTs with maximum transconductance up to 613mS/mm are achieved. The unity current gain cut-off frequency (fT) and the maximum oscillation frequency (fmax) are 36.9 and55.6 GHz, respectively. This device has the highest fTyet reported for 1.0- m-gate-length HEMTs grown on silicon byMOCVD. Also, this performance is comparable to that of similar GaAs-based mHEMTs. These are encouraging initial resultsleading to the manufacturing potential of integrated high-speed metamorphic devices for logic applications on silicon sub-strates by MOCVD.
基金supported by the CERG(Grant No. 615506) from the Research Grants Council of Hong Kong and Intel Corporation
文摘We present an InGaAs metamorphic high electron mobility transistor （mHEMT） grown using Metalorganic Chemical Vapor Deposition （MOCVD） on an n-type silicon substrate with the introduction of an effective multi-stage buffering scheme. Fabrication and performance of a high-frequency 0.3μm gate-length depletion-mode A10.s0In0.s0As/Ga0.47In0.53As mHEMT is re- ported for the first time. Using a combined optical and e-beam photolithography technology, submicron mHEMT devices on Si have been achieved. The non-alloyed ohmic contact resistance Rc was as low as 0.065 Ω-mm. A maximum transconductance up to 761 mS/ram was measured. The unity current gain cut-off frequency （fT） and the maximum oscillation frequency （fmax） were 72.8 and 74.5 GHz, respectively. This device has the highest fw yet reported for a 0.3-μm gate-length Si-based mHEMT grown using MOCVD. A high voltage gain, gm/gds, of 40.6 is observed in the device.
