Abstract:resist and backscattering from the substrate are negligible. Therefore, the proximity effect which puts severe limitations on electron beam fabrication of closely packed narrowlinewidth pattern is expected not to be a serious problem with ion-beam lithography. Encouraging results in this direction have also been quoted by Tarui. 5 These preliminary results are very encouraging and indicate that ion beams can be employed in lithography for the production and/or projection transfer of very-narrowlinewidth patter… Show more
“…Note that these photocurrents occur under anodic bias which is the normal operating potential range for photoanodes in a photoelectrochemical ce11. This is to be contrasted with the subband gap response observed in TiOs at cathodic bias (5) and subsequently explained as a photothermal effect (7). We have explored the potential behavior and the results are shown in Fig.…”
Section: Resultsmentioning
confidence: 91%
“…This is to be contrasted with the subband gap response observed in TiOs at cathodic bias (5) and subsequently explained as a photothermal effect (7). We have explored the potential behavior and the results are shown in Fig.…”
The response of TiO2 and SrTiO3 photoelectrodes to subband gap light has been explored as a function of numerous variables, including intensity and wavelength of light, applied potential, temperature, and electrolyte composition. The photoresponse is shown to be linear with light intensity, to depend on the square root of the applied potential, to occur only for hv > 2.2 eV, and to be independent of temperature and electrolyte composition. These results suggest a bulk excitation process involving impurity and defect-related states in the gaps of these semiconductors. A qualitative model is presented to account for the main features of this excitation process and to provide a basis for suggesting future experiments.
“…Note that these photocurrents occur under anodic bias which is the normal operating potential range for photoanodes in a photoelectrochemical ce11. This is to be contrasted with the subband gap response observed in TiOs at cathodic bias (5) and subsequently explained as a photothermal effect (7). We have explored the potential behavior and the results are shown in Fig.…”
Section: Resultsmentioning
confidence: 91%
“…This is to be contrasted with the subband gap response observed in TiOs at cathodic bias (5) and subsequently explained as a photothermal effect (7). We have explored the potential behavior and the results are shown in Fig.…”
The response of TiO2 and SrTiO3 photoelectrodes to subband gap light has been explored as a function of numerous variables, including intensity and wavelength of light, applied potential, temperature, and electrolyte composition. The photoresponse is shown to be linear with light intensity, to depend on the square root of the applied potential, to occur only for hv > 2.2 eV, and to be independent of temperature and electrolyte composition. These results suggest a bulk excitation process involving impurity and defect-related states in the gaps of these semiconductors. A qualitative model is presented to account for the main features of this excitation process and to provide a basis for suggesting future experiments.
“…By suitably casting thin films of TiO 2 particles on an electrode surface, it is possible to collect the electrons and generate current in a photoelectrochemical cell . The principle of photocatalysis has been widely employed in the development of solar cells and environmental remediation processes. − Under band gap excitation of the TiO 2 electrode, methanol is oxidized by the photogenerated holes, and the photogenerated electrons flow through the external circuit. In addition, Pt deposited on TiO 2 has long been accepted to increase the latter's photocatalytic performance. ,,− 1 Catalytic and Photocatalytic Oxidation of Methanol at a Pt/Ru and TiO 2 Modified Carbon Fiber Electrode …”
Section: Introductionmentioning
confidence: 99%
“…20 The principle of photocatalysis has been widely employed in the development of solar cells and environmental remediation processes. [20][21][22][23][24][25][26][27][28][29][30][31][32][33] Under band gap excitation of the TiO 2 electrode, methanol is oxidized by the photogenerated holes, and the photogenerated electrons flow through the external circuit. In addition, Pt deposited on TiO 2 has long been accepted to increase the latter's photocatalytic performance.…”
A hybrid carbon fiber electrode (CFE) consisting of TiO2 semiconductor photocatalyst and Pt-Ru catalyst has been developed to boost the performance of direct methanol fuel cells (DMFC). These two catalyst nanoparticles are deposited on opposite sides of the carbon fiber paper such that methanol oxidation is carried out catalytically on Pt-Ru and photocatalytically on TiO2 under UV-light irradiation. Since both catalysts carry out methanol oxidation independently, we observe an additive effect in the current generation. The carbon support fibers provide a large network to collect the electrons from both of these catalytic processes and thus assist in efficient current generation. In addition, TiO2 improves the performance of the Pt-Ru catalyst in dark, indicating possible surface area improvement or diminished poisoning effects. The concept of incorporating a photocatalyst provides new ways to minimize precious metal content and enhance the performance of DMFCs. At low catalyst loadings (0.15 mg/cm2) at 295 K, a 25% enhancement in the peak power density is observed upon illumination with light.
We have investigated the photocurrent induced by subbandgap light irradiation at the n-Si-aqueous electrolyte junction., The observed effect is shown to arise from optical processes involving interface states, and mainly from electron transitions from the filled interface states to the conduction band. The dependence of the photocurrent upon anodic voltage is accounted for quantitatively by considering the Schottky barrier lowering effect, already measured from the dark I-V characteristics. The dependence of the photocurrent upon photon energy enables us to extract a density of states curve for the occupied interface states. It suggests that these states are bound states on the semiconductor side, due to the coulomb potential of adsorbed ions. Complementary observations on oxidized and bandgap irradiated junctions are discussed and are found to fit well in the above picture.Experimental evidence for the role of interface states at the semiconductor-electrolyte junction has been brought in many instances, mostly through capacitance and recombination studies (1, 2). These techniques however, hardly permit a systematic investigation of interface states through the semiconductor gap. A true spectroscopy of these states might rather be obtained by observing the photocurrent induced by subbandgap optical transitions between these levels and the semiconductor bands (3, 4). This technique however, suffers from two drawbacks: (i) the expected effects are rather small; (ii) larger effects may be present in the same photon energy range, for example onset of bandgap absorption, transitions involving deep levels in the bulk or the space charge region, and also thermal effects (5). We present here the results of an investigation of the photocurrent induced by subbandgap light at the n-siliconaqueous electrolyte junction, where interface states are known to be present (2, 6). We show that they are indeed responsible for the observed effect and their energy distribution can be attained from the experimental data.
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