TiO 2 nanoribbons were synthesized hydrothermally via the reaction of TiO 2 particles and NaOH solution. Their photovoltaic properties were studied by surface photovoltage spectroscopy (SPS) and electric field-induced...TiO 2 nanoribbons were synthesized hydrothermally via the reaction of TiO 2 particles and NaOH solution. Their photovoltaic properties were studied by surface photovoltage spectroscopy (SPS) and electric field-induced surface photovoltage spectroscopy (FISPS). Under the external field, new photovoltaic response bands were found from 375 nm to 550 nm. It is suggested that these response bands resulted from the surface states, which can be ascribed to the formation of steps and kinks in the TiO 2 nanoribbons.展开更多
Alloy 690TT samples with four kinds of surface states were prepared： 1） ground to 400 grit; 2） ground to 1500 grit; 3） mechanically polished （MP） and 4） electro-polished （EP）. The surface morphologies and the...Alloy 690TT samples with four kinds of surface states were prepared： 1） ground to 400 grit; 2） ground to 1500 grit; 3） mechanically polished （MP） and 4） electro-polished （EP）. The surface morphologies and the surface skin layers＇ microstructures of these samples were characterized systematically using various methods and the effects of surface states on the oxidation behaviours of Alloy 690TT were also discussed. The results showed that surface roughness and micro-hardness decreased gradually from the ground to EP surfaces. The grains in the near-surface layers of the ground and MP surfaces had been refined and the residual strains were also very high. The dislocations on the ground surfaces were mainly parallel dislocation lines. The thickness of the superficial cold-worked layers decreased gradually from the ground surfaces to polished surfaces. The oxide morphologies and oxidation rate depended greatly on the surface states of samples. Cold-working by grinding treatments could benefit the outward diffusion of metallic atoms and the nucleation of surface oxides and then accelerate the growth of surface oxide films.展开更多
Oxidation of Alloy 690 TT samples either manually ground to 400 and 1500 grit, mechanically polished, or electropolished was performed in a solution of 1500 10 6B and 2.3 10 6Li with 2.5 10 6dissolved H2, at 325℃ and...Oxidation of Alloy 690 TT samples either manually ground to 400 and 1500 grit, mechanically polished, or electropolished was performed in a solution of 1500 10 6B and 2.3 10 6Li with 2.5 10 6dissolved H2, at 325℃ and 15.6 MPa for 60 days. The oxide films grown on samples with different surface states were analyzed using various techniques. Results show that a triple-layered structure was formed after immersion： an outermost layer with large scattered oxide particles rich in Fe and Ni, an intermediate layer with small compact oxide particles rich in Cr and Fe for the ground surfaces and loose needle-like oxides rich in Ni for the polished surfaces, and an inner layer with continuous Cr-rich oxides. The surface state was found to affect not only the surface morphology, but also the corrosion rate. Grinding accelerated the growth of protective oxide films such that the ground samples showed a lower oxidation rate than the polished ones.Samples of ground Alloy 690 TT showed superior resistance to intergranular attack（IGA）.展开更多
The relationship between A1GaN/GaN HEMT gate field plate （FP） and surface-state-related gate lag phenomena is investigated by two-dimensional numerical transient simulations to study the mechanism of the influence o...The relationship between A1GaN/GaN HEMT gate field plate （FP） and surface-state-related gate lag phenomena is investigated by two-dimensional numerical transient simulations to study the mechanism of the influence of FPs on current collapse. The simulations reveal that adding a field plate has a noticeable impact on the extent of current collapse while it has no influence on lapsed time. The FP is found to suppress current collapse through reducing the ionization probability of surface states by enhancing free hole accumulation next to the AIGaN surface between gate and drain.展开更多
Owing to their special three-dimensional network structure and high specific surface area,TiO2 submicrospheres have been widely used as electron conductors in photoanodes for solar cells.In recent years,utilization of...Owing to their special three-dimensional network structure and high specific surface area,TiO2 submicrospheres have been widely used as electron conductors in photoanodes for solar cells.In recent years,utilization of TiO2 submicrospheres in solar cells has greatly boosted the photovoltaic performance.Inevitably,however,numerous surface states in the TiO2 network affect electron transport.In this work,the surface states in TiO2 submicrospheres were thoroughly investigated by charge extraction methods,and the results were confirmed by the cyclic voltammetry method.The results showed that ammonia can effectively reduce the number of surface states in TiO2 submicrospheres.Furthermore,in-depth characterizations indicate that ammonia shifts the conduction band toward a more positive potential and improves the interfacial charge transfer.Moreover,charge recombination is effectively prevented.Overall,the cell performance is essentially dependent on the effect of the surface states,which affects the electron transfer and recombination process.展开更多
文摘TiO 2 nanoribbons were synthesized hydrothermally via the reaction of TiO 2 particles and NaOH solution. Their photovoltaic properties were studied by surface photovoltage spectroscopy (SPS) and electric field-induced surface photovoltage spectroscopy (FISPS). Under the external field, new photovoltaic response bands were found from 375 nm to 550 nm. It is suggested that these response bands resulted from the surface states, which can be ascribed to the formation of steps and kinks in the TiO 2 nanoribbons.
基金supported by the Special Funds for the Major State Basic ResearchProjects under grant No. G2011CB610502the National Natural Science Foundation of China under grant No. 51025104.
文摘Alloy 690TT samples with four kinds of surface states were prepared： 1） ground to 400 grit; 2） ground to 1500 grit; 3） mechanically polished （MP） and 4） electro-polished （EP）. The surface morphologies and the surface skin layers＇ microstructures of these samples were characterized systematically using various methods and the effects of surface states on the oxidation behaviours of Alloy 690TT were also discussed. The results showed that surface roughness and micro-hardness decreased gradually from the ground to EP surfaces. The grains in the near-surface layers of the ground and MP surfaces had been refined and the residual strains were also very high. The dislocations on the ground surfaces were mainly parallel dislocation lines. The thickness of the superficial cold-worked layers decreased gradually from the ground surfaces to polished surfaces. The oxide morphologies and oxidation rate depended greatly on the surface states of samples. Cold-working by grinding treatments could benefit the outward diffusion of metallic atoms and the nucleation of surface oxides and then accelerate the growth of surface oxide films.
基金supported by the Special Funds for the National Basic Research Program of China (No. 2011CB610502)the National Science and Technology Major Project (No. 2011ZX06004-009)the National Natural Science Foundation of China (No. 51025104)
文摘Oxidation of Alloy 690 TT samples either manually ground to 400 and 1500 grit, mechanically polished, or electropolished was performed in a solution of 1500 10 6B and 2.3 10 6Li with 2.5 10 6dissolved H2, at 325℃ and 15.6 MPa for 60 days. The oxide films grown on samples with different surface states were analyzed using various techniques. Results show that a triple-layered structure was formed after immersion： an outermost layer with large scattered oxide particles rich in Fe and Ni, an intermediate layer with small compact oxide particles rich in Cr and Fe for the ground surfaces and loose needle-like oxides rich in Ni for the polished surfaces, and an inner layer with continuous Cr-rich oxides. The surface state was found to affect not only the surface morphology, but also the corrosion rate. Grinding accelerated the growth of protective oxide films such that the ground samples showed a lower oxidation rate than the polished ones.Samples of ground Alloy 690 TT showed superior resistance to intergranular attack（IGA）.
文摘The relationship between A1GaN/GaN HEMT gate field plate （FP） and surface-state-related gate lag phenomena is investigated by two-dimensional numerical transient simulations to study the mechanism of the influence of FPs on current collapse. The simulations reveal that adding a field plate has a noticeable impact on the extent of current collapse while it has no influence on lapsed time. The FP is found to suppress current collapse through reducing the ionization probability of surface states by enhancing free hole accumulation next to the AIGaN surface between gate and drain.
基金This work was supported by the National High-tech R＆D Program of China （No. 2015AA050602）, the External Cooperation Program of BIC, Chinese Academy of Sciences （No. GJHZ1607）, the National Natural Science Foundation of China （Nos. U1205112, 51572080 and 21273242） and Natural Science Foundation of Anhui Province （No. 1508085SMF224）.
文摘Owing to their special three-dimensional network structure and high specific surface area,TiO2 submicrospheres have been widely used as electron conductors in photoanodes for solar cells.In recent years,utilization of TiO2 submicrospheres in solar cells has greatly boosted the photovoltaic performance.Inevitably,however,numerous surface states in the TiO2 network affect electron transport.In this work,the surface states in TiO2 submicrospheres were thoroughly investigated by charge extraction methods,and the results were confirmed by the cyclic voltammetry method.The results showed that ammonia can effectively reduce the number of surface states in TiO2 submicrospheres.Furthermore,in-depth characterizations indicate that ammonia shifts the conduction band toward a more positive potential and improves the interfacial charge transfer.Moreover,charge recombination is effectively prevented.Overall,the cell performance is essentially dependent on the effect of the surface states,which affects the electron transfer and recombination process.
