ZnO:Al (AZO) thin films were deposited on glass substrates by RF magnetron sputtering at room temperature and post-annealed in rapid thermal annealing (RTA) system. The effect of post-annealing temperature on the structural, optical, and electrical properties was investigated. As the post-annealing temperature increased, electrical conductivity is deteriorated due to a decrease in the mobility or carrier concentration, gradually. According to X-ray photoelectron spectroscopy (XPS) analysis, the behavior of mobility and carrier concentration is attributed to increase the O2 absorption on film surface, which act as rising the barrier potential at the low post-annealing temperature (200 °C) and reducing the density of donor-like defects at the high post-annealing temperature (400 °C). In case of post-annealing, the minimization of O2 absorption is a very important factor to obtain better electrical properties. 相似文献
Al doped ZnO has been explored as a viable alternative to indium thin oxide, which is usually used as transparent electrodes' coverage but is expensive. Homogenous and durable ZnO:Al layers on glass have been obtained in radio frequency magnetron sputtering system by adjusting optimized deposition parameters, using ZnO ceramic target with 2?wt% Al2O3. Then, after growth process, annealing treatment has been introduced in order to improve the quality of the layers. Structural, electrical and optical properties of the obtained ZnO:Al layers are presented and discussed. From the application point of view, the best results (sheet resistance of 24 Ω/sq and transparency well above 85%) were achieved after annealing in 300?°C. 相似文献
We numerically investigate the role of antireflection (AR) coatings, composed of SiO2 and/or ZnO, in suppression of interfacial reflections in the presence of the transparent conducting oxide, Al-doped ZnO (AZO). Three structures are simulated: (a) AR coatings in organic light-emitting diodes (OLEDs) and flat panel displays, (b) AR coating located between the glass and the AZO, and (c) same as the case b except the involvement of another AR coating between the AZO and the amorphous silicon layers. The weighted average transmittance according to the AM1.5 solar spectrum, the photovoltaic transmittance (Tpv), suggests that there is no evident difference between the structures a and b, especially when the layer number of AR coatings is less than three. An effective way to improve Tpv is presented in the structure c, where Tpv is increased from 73.54% to 76.32% with a three-layered AR coating located between AZO and a-Si. It implies that the suppression of interfacial reflections, resulting from the considerable mismatch of refractive indices at the interface of AZO and a-Si, would benefit the efficiency improvement of silicon thin-film solar cells. 相似文献
A very thin (250 nm), highly conductive (annealed), non‐texturized DC‐sputtered aluminum‐doped zinc oxide layer (ZnO:Al) deposited on a textured glass is used as substrate for thin‐film silicon solar cells. Compared to the classical approach, where wet‐chemically texturized ZnO:Al on planar glass is used, this approach allows a reduction in the as‐deposited ZnO:Al thickness of almost 70% while at the same time, thanks to the good light trapping capability of the glass texture the efficiency of the cells was maintained at the high level of 10.9%.
Transparent conducting thin films of ZnO:Al (Al-doped ZnO, AZO) were prepared via pulsed DC magnetron sputtering with good transparency and relatively lower resistivity. The AZO films with 800 nm in thickness were deposited on soda-lime glass substrates keeping at 473 K under 0.4 Pa working pressure, 150 W power, 100 μs duty time, 5 μs pulse reverse time, 10 kHz pulse frequency and 95% duty cycle. The as-deposited AZO thin films has resistivity of 6.39 × 10−4 Ω cm measured at room temperature with average visible optical transmittance, Ttotal of 81.9% under which the carrier concentration and mobility were 1.95 × 1021 cm−3 and 5.02 cm2 V−1 s−1, respectively. The films were further etched in different aqueous solutions, 0.5% HCl, 5% oxalic acid, 33% KOH, to conform light scattering properties. The resultant films etched in 0.5% HCl solution for 30 s exhibited high Ttotal = 78.4% with haze value, HT = 0.1 and good electrical properties, ρ = 8.5 × 10−4 Ω cm while those etched in 5% oxalic acid for 150 s had desirable HT = 0.2 and relatively low electrical resistivity, ρ = 7.9 × 10−4 Ω cm. However, the visible transmittance, Ttotal was declined to 72.1%. 相似文献
The metal-oxide-semiconductor (MOS) field effect transistor (FET) using ‘oxidized μ c-Si/ultrathin oxide’ gate structure was studied. It was found that this structure shows negative differential resistance behavior, which can be explained by the Coulomb blockade effect of trapped carriers and immediate tunneling into and tunneling out with gate bias variation. The requirements for the device with this structure showing negative differential resistance behavior are based on very weak resistive coupling between floating gate and channel. They are the thinness of the tunnel oxide film, the thickness ratio of the upper oxidized film and the tunnel oxide, and the channel threshold voltage. MOSFET with this gate structure is proposed as a new negative differential resistance device. 相似文献
A 1.57 μm eye-safe laser is realized by placing a KTP crystal into a diode-end-pumped, acousto-optically (AO) Q-switched Nd:YVO4 laser. For the first time, the 1.06 μm pumping laser with a concave–concave cavity is used to lower the threshold of the intracavity-pumped optical parametric oscillator (IPOPO). The pumping threshold and output characteristics of the OPO are analyzed by changing repetition rate of the AO Q-switch and output mirrors with different transmissivity at 1.57 μm. The results show that the pumping threshold will decrease with the lower output transmissivity and the lower repetition rate, but the narrower output pulse width can be obtained with the higher output transmissivity. 相似文献
We report a high-power continuous-wave(cw) diode-pumped efficient 1.34 μm Nd:YVO4 laser. The laser properties of a low Nd3+-doped concentration of the Nd:YVO4 crystal operating at 1.34 μm formed with a simple plane-concave cavity have been demonstrated. With the incident pump power of 22 W, an output power of 8.24 W was obtained, giving an optical conversion efficiency of 37.5% and slope efficiency of 40%. The thermal effects of cw end-pumped solid-state lasers were studied. 相似文献
We investigated InAs-Dots-in-a-well structures emitting near 1.3 μm by bright field and Z-contrast mode in a scanning transmission electron microscope. The chemically sensitive Z-contrast mode is found to give direct information on the actual position of the InAs-Dots inside the embedding well, while the bright field mode monitors the strain fields. Comparing a series of structures, we found that the most symmetric design is realized by an nominally asymmetric growth. These symmetric structures exhibit the best performance with respect to photoluminescence spectra and laser threshold current density. 相似文献
Phosphorous-doped hydrogenated nanocrystalline silicon oxide(n-nc-SiO_x:H) films are prepared via radio frequency plasma enhanced chemical vapor deposition(RF-PECVD). Increasing deposition power during n-nc-SiO_x:H film growth process can enhance the formation of nanocrystalline and obtain a uniform microstructure of n-nc-SiO_x:H film. In addition,in 20 s interval before increasing the deposition power, high density small grains are formed in amorphous SiO_x matrix with higher crystalline volume fraction(I_c) and have a lower lateral conductivity. This uniform microstructure indicates that the higher Ic can leads to better vertical conductivity, lower refractive index, wider optical band-gap. It improves the back reflection in a-Si:H/a-SiGe:H tandem solar cells acting as an n-nc-SiO_x:H back reflector prepared by the gradient power during deposition. Compared with the sample with SiO_x back reflector, with a constant power used in deposition process,the sample with gradient power SiO_x back reflector can enhance the total short-circuit current density(Jsc) and the initial efficiency of a-Si:H/a-SiGe:H tandem solar cells by 8.3% and 15.5%, respectively. 相似文献
Measurement of concentration distributions of suspended particles in a micro-channel is one of the most crucial necessities in the area of Lab-on-a-chip to be used for various bio-chemical applications. One most feasible way to measure the concentration field in the micro-channel is using μ-LIF (micro-scale laser-induced fluorescence) method. However, an accurate concentration field at a given cross-plane in a micro-channel has not been successfully achieved so far due to various limitations in the light illumination and fluorescence signal detection. The present study demonstrates a novel method to provide an ultra-thin laser sheet beam having 5 μm thickness using a micro-focus laser line generator. The laser sheet beam illuminates an exact plane of concentration measurement field to increase the signal-to-noise ratio and considerably reduce the depth uncertainty.Nile Blue A was used as fluorescent dye for the present LIF measurement. The enhancement of the fluorescent intensity signals was performed by a solvent mixture of water (95%) and ethanol (EtOH)/methanol (MeOH) (5%) mixture. To reduce the rms errors resulting from the CCD electronic noise and other sources, an expansion of grid size was attempted from 1×1 to 3×3 or 5×5 pixel data windows and the pertinent signal-to-noise level has been noticeably increased accordingly. 相似文献
Contrary to conventional light emitting diodes for visible and very near infrared utilizing interband (ω>Eg) luminescence, the longer infrared emitting diodes (LIREDs) we describe here utilize intraband (ω<Eg) electron transitions and emit beyond the fundamental absorption range of the material used. Made of indirect band gap semiconductors (like Ge, Si) and, therefore, free from the Auger recombination impact, LIREDs efficiently operate at higher temperatures (T>300 K) in the longer wavelength atmospheric window (8–12 μm). Electrically modulated power emitted is comparable to that for black body sources whereas shorter rise–fall times are due to recombination processes (200 μs) and not dependent on pixel thermal mass and thermal conduction. LIREDs can be made of different semiconductor structures provided the controllable modulation of free carrier concentration in the device base is achieved. The main parameters of Ge based LIREDs under injection mode are reported. 相似文献
We fabricated point-contacted a-Si:H(p)/c-Si(n) heterojunction solar cells using patterned SiO2 and investigated their electrical properties using the light current–voltage (I–V) curve and Suns-Voc measurements. The light I–V curves showed bias-dependent changes according to the applied voltage in the point-contacted cells, especially in the samples with a long distance between the point-contacted junctions. The Suns-Voc measurements showed that the bias-dependence of the light I–V curves did not originate from the recombination in the SiO2/Si or a-Si:H(p)/c-Si(n) interface, but from the series resistances. It is possible to explain the bias-dependent light I–V curve in terms of the conductivity of a-Si:H(p) and difference in the electrical contact properties between a-Si:H(p), ZnO and c-Si(n). These results mean that the electrical properties of the a-Si:H(p) layer and the contact properties with this layer are also critical to obtain a high Jsc and fill factor in n-type based Si heterojunction solar cells. 相似文献