Effect Of Buffer Layer Thickness Research Articles

On the Impact of Cadmium Sulfide Layer Thickness on Kesterite Photodetector Performance

Kesterites are currently viewed as one of the most promising candidates for earth abundant and benign elements to substitute critical raw materials in photovoltaic technologies and may also be suitable for low‐noise, room‐temperature, self‐powered photodetectors. However, while the impact of buffer layers on kesterite solar cell efficiency has been an active area of investigation, links between photodetector performance and intermediate layers are yet to be addressed. Herein, the impact of cadmium sulfide buffer layers on the performance of kesterite (Cu2ZnSnS4) photodetectors is probed. Specifically, the effect of buffer layer thickness on various photodetector performance metrices is clarified, including noise current, spectral responsivity, noise equivalent power, frequency response, and specific detectivity. Devices with a 100 nm cadmium sulfide layer perform the best, achieving a linear dynamic range of 180 dB and frequency responses in the range of tens of kHz. The key loss mechanisms are identified, and it is found that the photodetector performance to be primarily limited by shunt resistance‐induced thermal noise and defect‐induced nonradiative losses. Furthermore, we estimate the upper radiative limit of specific detectivity to be approximately Jones. Our results highlight the potential of kesterites to be used as an interesting earth abundant candidate for photodetection applications.

Analysis of different buffer layers on CuO based solar cells using SCAPS-1D

We have used SCAPS-1D to do simulations on CuO based solar cells using ZnO, TiO2, CdS and ZnSe as buffer layers. The solar cell characteristics are analysed by varying different material properties. The CuO/ZnO based solar cell showed highest efficiency ~20%. The interface defect however impacts the efficiency of this solar cell significantly. The interface defect and buffer layer thickness has shown little impact on the TiO2 and ZnSe buffer layer based solar cell. Further, we have optimized the impact of absorber layer thickness, carrier concentration and absorber defect as well. The effect of buffer layer thickness and electron affinity has also been investigated. Further, we have tried to understand the effect of temperature on the performance of these solar cells. The increase in temperature has resulted in decreased efficiency attributing to increased recombination rate.

Efficiency enhancement by simulation method of Copper Antimony Disulfide thin film based solar cells

In this work we investigated by SCAPS-1D several effects on the performance of CuSbS2 based solar cell. The simulated baseline structure is Al/ZnO:Al/i-ZnO/CdS/CuSbS2/Mo which is inherited from the structure of CIGS based solar cells. We studied the effect of buffer layer thickness which gave us as an optimum value 0.1 µm. As for CdS carrier density 1018 cm−3 is the optimum value. After that, temperature effect has been checked too it is demonstrated that increasing temperature lead to lower the cell performance. In addition, the effect of work function showed that Molybdenum is a good element for back contact. Then, conduction band offset has been investigated. It is demonstrated that this value is critical. The efficiency increased from 4.8% to 15.74% for − 0.8 eV and − 0.2 eV CBO values. Finally and in order to reduce the toxicity of the device we decided to design cadmium free solar cells. SnS2 and In2S3 are chosen as buffer layer candidate. They showed good performance especially SnS2 with an efficiency of 16.21%.

Synthetic analysis on the IZTO thin films deposited on various plastic substrates with the buffer layer

Buffer layers, such as SiO2, may prevent impurities from permeating into the depositing film. Thus, the effects of buffer layer thickness on indium-zinc-tin oxide (IZTO) thin films were investigated. IZTO thin films are applied to transparent conductive oxide, and SiO2 is used as a material for the buffer layer. Before depositing the IZTO by RF magnetron sputtering, the SiO2 buffer layers were deposited on different plastic substrates, such as polyether sulfone, polyethylene terephthalate, and polyethylene naphthalate (PEN), by plasma enhanced chemical vapor deposition. The resulting structural, morphological, electrical, and optical properties were measured and analyzed. By using the obtained values of the electrical and optical properties, the figure of merit for transparent devices designed by Haacke was calculated. As a result, we conclude that the IZTO thin film deposited on a PEN substrate with a 30 nm thick SiO2 buffer layer has the finest properties, which are a resistivity of 2.13 × 10−3 Ω-cm, sheet resistance of 8.875 Ω sq−1, Hall mobility of 5.99 cm2 V−1 s−1, carrier concentration of 3.671 × 1021 cm−3, and transmittance of 80.26% at 550 nm. In addition, the figure of merit calculated for this sample was 12.50 × 10−3/Ω. These results indicate that the proposed structure is suitable for flexible display devices and flexible solar cells.

Buffer layer replacement: A method for increasing the conversion efficiency of CIGS thin film solar cells

The performance of the buffer layer of CIGS thin film solar cell was optimized using SCAPS software to improve the conversion efficiency. In the first step, the validity of empirical and simulation models were verified. After that, four buffer layers of InS, ZnS, ZnO and ZnSe were substituted with CdS in the Glass/Mo/CIGS/CdS/ZnO/ZnO:Al nanostructure. The results indicated that the Zn-based compounds are proper substitute buffer layers with similar electronic and physical properties due to higher band gap than CdS. Next, the effect of buffer layer thickness was investigated and the optimum thicknesses of buffer layers was achieved. Results revealed that zinc selenide with efficiency of 20.07% can be an appropriate alternative buffer layer for CdS. Also, it is shown that by optimizing the buffer layer thicknesses, the solar cell efficiency raises, mainly due to increase in fill factor.

Effects of Buffer-layer Thickness and Active-layer Growth Temperature on ZnO Nanocrystalline Thin Films Grown by Molecular Beam Epitaxy

Effects of Buffer-layer Thickness and Active-layer Growth Temperature on ZnO Nanocrystalline Thin Films Grown by Molecular Beam Epitaxy

Effect of Buffer Layer Thickness on Fatigue and Residual Stress of Welded High-Strength Low-Alloy

The present work dealt with the fatigue and residual stress (RS) effects of a soft buffer layer (BL) between the parent metal and the weld metal (WM) on welded high-strength low-alloy (HSLA) steel. Six strategies were pursued by varying BL thickness and changing U-notch position with respect to the WM in extended-compact tension specimen. The U-notch position was changed to study the effect of welding RS field, acting along the fatigue crack growth path. The welded HSLAs with BLs strategies were compared to the specimens without BLs strategies, before and after releasing RS respectively. The results demonstrated that the incorporation of a thin BL of 4 mm significantly reduced the fatigue crack growth rate (da/dN) when the RS in the welded HSLA was released by machining a U-notch in the WM. A thick BL of 10 mm was found to be beneficial to fatigue resistance when a U-notch was in the PM.

Effects of buffer layer thickness on properties of ZnO thin films grown on porous silicon by plasma-assisted molecular beam epitaxy

ZnO thin films with different buffer layer thicknesses were grown on Si and porous silicon (PS) by plasma-assisted molecular beam epitaxy (PA-MBE). The effects of PS and buffer layer thickness on the structural and optical properties of ZnO thin films were investigated by atomic force microscopy (AFM), scanning electron microscopy (SEM), X-ray diffraction (XRD), and photoluminescence (PL). The ZnO buffer layers, the intensity of the (002) diffraction peak for the ZnO thin films and its full width at half maximum (FWHM) decreased with an increase in the thickness of the ZnO buffer layers, indicating an improvement in the crystal quality of the films. On introducing PS as a substrate, the grain sizes of the ZnO thin films became larger and their residual stress could be relaxed compared with the ZnO thin films grown on Si. The intensity ratio of the ultraviolet (UV) to visible emission peak in the PL spectra of the ZnO thin films increased with an increase in buffer layer thickness. Stronger and narrower UV emission peaks were observed for ZnO thin films grown on PS. Their structural and optical properties were enhanced by increasing the buffer layer thickness. In addition, introduction of PS as a substrate enhanced the structural and optical properties of the ZnO thin films and also suppressed Fabry–Perot interference.

Effect of MgO buffer layer thickness on the electrical properties of MgZnO thin film transistors fabricated by plasma assisted molecular beam epitaxy

We report the fabrication and electrical characteristics of thin film transistors based on MgZnO thin films with different thicknesses of MgO buffer layer. The MgZnO thin films with MgO buffer layers were grown on SiO 2/p-Si substrates by plasma assisted molecular beam epitaxy. The effects of the buffer layer thickness on the structural properties of MgZnO films are investigated by X-ray diffraction, and the results show that the crystal quality of the MgZnO film is enhanced with 4 nm MgO buffer layer. The MgZnO TFT with 4 nm MgO buffer layer exhibits an n-type enhancement mode characteristics with a field effect mobility of 1.85 cm 2/V s, a threshold voltage of 27.6 V and an on/off ratio of above 10 6.

Effect of Buffer Layer Thickness on the Growth Properties of Hydrothermally Grown ZnO Nanorods

We investigated the effect of ZnO buffer layer thickness on the growth of hydrothermally grown ZnO nanorods. A series of ZnO buffer layers with different thicknesses was deposited on a p-Si (111) substrate using a co-sputtering system. After annealing the ZnO buffer layer, ZnO nanorods grown were grown hydrothermally at 95 degrees C. Unlike ZnO nanorods grown on as-deposited ZnO buffer layer, the diameter and length of ZnO nanorods grown on annealed ZnO buffer layers can be controlled. The structural and optical properties of ZnO nanorods grown on annealed ZnO buffer layers were analyzed by field-emission scanning electron microscopy, X-ray diffraction, and photoluminescence. The influence of ZnO buffer layer thickness on ZnO nanorods growth is discussed.

Extremely thin absorber layer solar cells on zinc oxide nanorods by chemical spray

ZnO rod/In 2S 3/CuInS 2 type ETA-cells were prepared by in-line chemical spray pyrolysis method. Effects of buffer layer thickness and ZnO nanorod length (500–1000 nm) were studied by means of SEM, I– V dependencies and EQE spectra. Conformal layer of In 2S 3, obtained by spray of solution with pH=4.8, effectively protects ZnO nanorods from dissolution during the spray of acidic solutions. Increasing In 2S 3 layer thickness reduces fluctuations of the cell output parameters, and increases V OC and FF; however, at certain thickness induces losses due to light absorption. The highest conversion efficiency 4.17% at AM1.5 was recorded from small contact area of the cell based on rods with length of 600 nm. Perspectives for further development are discussed.

Effect of buffer layer thickness and epilayer growth temperature on crystalline quality of InAs0.9Sb0.1 grown by MOCVD

InAs0.9Sb0.1 epilayers are grown on GaAs (001) substrates by metal organic chemical vapor deposition (MOCVD). In order to relax compressive strain caused by lattice mismatch between InAs0.9Sb0.1 and GaAs, we employ a two-step growth method in which low temperature (430 °C) InAs0.9Sb0.1 buffer layers with different thicknesses are introduced into the structure. Effect of the buffer layer thickness and the epilayer's growth temperature on crystalline quality of the epilayer is investigated, respectively. It is clear that there are strip pyramids paralleling with each other on most surface of the samples. The crystalline quality gets well obviously when the buffer layer thickness change from 0 to 50 nm, but it gets worse when the buffer layer thickness increases to 100 nm. It is also shown that the crystalline quality of the epilayer is improved obviously when the epilayer is grown at 500 °C, and it gets worse when the growth temperature decreases or increases.

Growth of high quality rutile TiO 2 thin film using ZnO buffer layer on Si(100) substrate

The TiO 2 rutile thin films were grown on Si(100) substrates with ZnO buffer layer at a substrate temperature of 500 °C by radio frequency (rf) magnetron sputtering. In order to investigate the effect of buffer layer thickness on the growth of the TiO 2 film, the ZnO buffer layers were deposited in the thickness range of 70–150 nm. The thickness of the TiO 2 films was about 200 nm identical for all the samples. The crystal structure of the buffer layers and the TiO 2 thin films was characterized by X-ray diffractometer (XRD). The XRD spectra confirmed that TiO 2 rutile film with high crystalline quality was achieved on the ZnO buffer layer, which had a great relation to the improvement of the crystalline quality of the ZnO buffer layer. The surface morphologies of the TiO 2 rutile thin films were evaluated by atomic force microscopy (AFM). The roughness of the TiO 2 thin films became smoother as the thickness of the ZnO buffer layer increased.

Effects of buffer layer thickness on growth and properties of ZnO nanorods grown bymetalorganic chemical vapour deposition

We investigated the effect of the buffer layer thickness on the structural and opticalproperties of ZnO nanorods grown on Si substrates by metalorganic chemical vapourdeposition. Increasing the thickness of the buffer layer significantly enhanced the verticalalignment and density of the nanorods. The ZnO nanorods grown on the buffer layer with athickness exceeding 500 nm were inclined on the substrate surface, due to theformation of a rugged morphology with a pyramidal shape on the surface of the bufferlayer, which was attributed to the surface undulation resulting from the increasedtensile strain. This inclination also resulted in a decrease in the intensity of the(0002)ZnO diffraction peak and the ultraviolet emission peak. This paper discusses the microstructuralproperties and growth mechanism of the ZnO nanorods on buffer layers with variousthicknesses.

Effects of buffer layer thickness and strain on the dielectric properties of epitaxial SrTiO3 thin films

The dielectric behavior of SrTiO3 (STO) thin films grown epitaxially on different substrates using pulsed laser ablation is reported in this article. The thickness of the SrRuO3 buffer layer, serving as an electrode, was varied from 500 to 5000 Å, to study the dependence of dielectric properties of the STO films on the buffer layer thickness. Strains introduced during the high-temperature deposition of these films, seem to greatly influence the dielectric behavior observed in them in the form of loss peaks. This article also reports the results of tunability and the results of dielectric measurements are correlated to the strain in the films.

Interfacial stability and structure in InAs/GaAs(111)A heteroepitaxy: Effects of buffer layer thickness and film compositional grading

Interfacial stability and the morphology of the epitaxial film surface have been studied in InAs/GaAs(111)A heteroepitaxy based on atomistic simulations and scanning tunneling microscopy. Effects of buffer layer thickness were examined by analyzing two heteroepitaxial systems consisting of thin and thick GaAs buffer layers. In both cases, one monolayer of In0.50Ga0.50As is grown initially on the buffer layer prior to InAs growth. Our results indicate that film compositional grading and the resulting segregation of In atoms at defects in the semicoherent interface can be used effectively in conjunction with the mechanical compliance of thin buffer layers to delay the completion of the coherent-to-semicoherent interfacial transition.

Effects of buffer layer thickness and film compositional grading on strain relaxation kinetics in InAs/GaAs(111)A heteroepitaxy

The effects on the strain relaxation kinetics of a thin buffer layer's mechanical response and of the epitaxial film compositional grading are investigated in the epitaxial growth of InAs on GaAs(111)A. Two heteroepitaxial systems are analyzed, consisting of thin and thick GaAs buffer layers grown on GaAs(111)A epi-ready substrates. In both cases, one monolayer of In 0.50Ga 0.50As is grown initially on the buffer layer followed by growth of several monolayers of InAs. In both systems, strain relaxation in the grown film is measured as a function of film thickness. The experimental measurements are described successfully by a phenomenological mean-field theoretical analysis. Our results support that the mechanical response of a thin buffer layer is similar to that of a thin compliant substrate that is unconstrained at its base. Furthermore, our results indicate that the mechanical behavior of a thin buffer layer can be used in conjunction with film compositional grading toward strain relaxation engineering in semiconductor heteroepitaxy.