Papers by Keyword: Photocurrent

Abstract: A series of GaAsBi/GaAs multiple quantum well p-i-n diodes was grown using molecular beam epitaxy and the opto-electrical characterisations are presented. The result shows that devices experience low carrier extractions when light is absorbed due to hole trapping in the valence band. Carrier enhancement can be achieved by applying slight reverse bias when the measurement was taken. The absorption coefficient of the devices is confirmed to be similar with other Bi-based work. GaAsBi/GaAs multiple quantum well do have a lot of room for improvement especially on growth, structure and strain level of the material. If these components can be catered, GaAsBi can be a competitive alternative for 1 eV junction in multiple junction solar cells.

Abstract: By the method of thermal oxidation of n-type CuInSe2 crystals, n - n+ structures with a maximum absolute current photosensitivity of up to 10 mA / W were obtained at low rectification and no-load photovoltage. The used modes of thermal oxidation led to the formation of n-type layers on the surface of the n-CuInSe2 plates, the resistivity of which is 2-2.5 times higher concerning the initial substance. Measurements of the stationary current-voltage characteristics have shown that the structures obtained have a slight rectification K. All the structures obtained exhibit photosensitivity, which dominates when illuminated from the side of the layer in the spectral region of about 1 eV. The optimization of the process can reveal the technological possibilities of a significant improvement in the rectifying properties of isotypic structures based on CuInSe2.

Abstract: By fixing Quantum Dots (QDs) on gold electrodes with dithiol compounds, a novel Ascorbic Acid sensor without any redox mediator was desighed. First, the fabrication process of sensor was described.Sencond, the characteristics of the sensor were investigated. Third,the sensor was tested in Ascorbic Acid solutions of different concentrations.From the results,it shows that the performance of photoelectrochemical sensor were influenced by the bias voltage and the amplitude of photocurrent changed with the Ascorbic Acid concentration linearly in detection range.

Abstract: In this paper, a novel photoelectrochemical sensor based on doped quantum dots (QDs) under various bias voltages was designed, first, photoelectrochemical sensors were designed for detection of chemical solution concentration. Second, the fabrication processes of doped QDs based sensors were described, third, doped QDs based sensors were tested under different applied potentials and light sources to show different measurement characteristics. From the experimental results, it can be concluded that the doped QDs based sensors designed under-300mV applied potential and 365nm light source show the best performance.

Abstract: The present study employs NaOH as an oxygen source in fluorinated ethylene glycol (EG) electrolyte for the formation of titanium dioxide nanotube arrays (TiO₂ NTs) by anodic process. The nanotube formed were 125 nm in diameter with length of ~ 7 µm after 30 min of anodization. They were then annealed to study the effect of annealing temperature on the photocurrent generated by the TiO₂ NTs. It is found that TiO₂ NTs annealed at 400 °C has the highest photocurrent (0.716 mA cm^-2 at 0.5 V vs Ag/AgCl). This is attributed to the crystallinity (mostly anatase) of the TiO₂ NTs as well as the nanotubular structure which retains at this temperature but not at higher temperature.

Abstract: In this paper we have studied the connection between crystal quality and electrical transport in 4H-SiC by simultaneous micro-photoluminescence (μPL) and photocurrent (PC) measurements. We have used a focused HeCd laser at 325 nm (i.e. above bandgap) to measure with a spatial resolution of few microns both the μPL spectra and the I-V characteristics in 4H-SiC/Ni Schottky diodes. We found that the PC signal acquired along a defect can give information on its spatial distribution in depth. The minority carrier lifetime has been also estimated and its dependence on the emission wavelength has been determined for several stacking faults.

Abstract: Commercial 4H-SiC p⁺n structures with an uncompensated donor concentration (N_d-N_a) of ~1.5∙10¹⁵ cm^-3 in the n-type epitaxial layer are studied. The measurement of the photocurrent, electron beam induced current and transient switching characteristics (from forward to reverse voltage), altogether showed that the value of the hole diffusion length, about 2 μm at room temperature, increases to at least 7 μm at 620 K.

Abstract: In this paper we have studied the connection between crystal quality and electrical transport in 4H-SiC by simultaneous micro-photoluminescence (μPL) and micro-photocurrent (μPC) measurements. We have used a focused HeCd laser at 325nm (i.e. above bandgap) to measure with a spatial resolution of few microns both the μPL spectra and the I-V characteristics in 4H-SiC/NiSi Schottky diodes. We found that extended defects exhibiting a photoluminescence peak located at 2.9eV (i.e single Shockley or bar shaped stacking faults) can produce an increase of the measured PC whereas other defects, such as the (4,4) stacking fault, can be considered as ‘killer defects’, strongly reducing the photocurrent.

Abstract: Cerium oxide (CeO₂) or known as ceria were deposited on titanium dioxide, TiO₂, nanotubes by electrodeposition process as to produce hybrid materials that can generate photocurrent. The electrodeposition process is done by using 0.1 M cerium chloride mixed with 0.1 M ammonium acetate as ligands to promote stability complexes in a standard two electrode bath. Voltage and pH were controlled to ensure the most optimum condition of cerium oxide deposition. Samples were then annealed at different temperatures. Photocurrent results indicate that annealed sample at 450°C shows the best photocurrent due to high degree of anatase and cubic crystallinity.

Abstract: Anodisation of iron foil was done to produce anodic film with nanoporous structure. The effect of anodic voltage on the morphology of the anodic oxide formed was investigated. Anodic film formed on iron foil anodised at 10 V is rather compact no obvious pores. Pores can be detected on oxide anodised at 30 V despite not very uniform. For foil anodised at 50 V, 1.8 µm thick anodic layer which consisted of uniform circular pores is observed. This film was then annealed at 450°C for 3 h in air as to induce crystallinity. The annealed nanoporous film exhibits a light illuminated photocurrent of 0.45 mA in 1 M NaOH + H₂O₂ solution.