In this work, optical–structural and morphological behavior when Nd is incorporated into ZnO is studied. ZnO and Nd-doped ZnO (ZnO-Nd) films were deposited at 900 °C on Silicon n-type substrates ...(100) by using the Hot Filament Chemical Vapor Deposition (HFCVD) technique. For this, pellets were made by from powders of ZnO(s) and a mixture of ZnO(s):Nd(OH)3(s). The weight percent of the mixture ZnO:Nd(OH)3 in the pellet is 1:3. The gaseous precursor generation was carried out by chemical decomposition of the pellets using atomic hydrogen which was produced by a tungsten filament at 2000 °C. For the ZnO film, diffraction planes (100), (002), (101), (102), (110), and (103) were found by XRD. For the ZnO-Nd film, its planes are displaced, indicating the incorporation of Nd into the ZnO. EDS was used to confirm the Nd in the ZnO-Nd film with an atomic concentration (at%) of Nd = 10.79. An improvement in photoluminescence is observed for the ZnO-Nd film; this improvement is attributed to an increase in oxygen vacancies due to the presence of Nd. The important thing about this study is that by the HFCVD method, ZnO-Nd films can be obtained easily and with very short times; in addition, some oxide compounds can be obtained individually as initial precursors, which reduces the cost compared to other techniques. Something interesting is that the incorporation of Nd into ZnO by this method has not yet been studied, and depending on the method used, the PL of ZnO with Nd can increase or decrease, and by the HFCVD method the PL of the ZnO film, when Nd is incorporated, increases more than 15 times compared to the ZnO film.
P-type semiconducting cupric oxide (CuO) was formed by thermal oxidation of copper (Cu) sheets. Oxidation variables such as temperature, oxidation time, and oxidation atmosphere were controlled with ...the aim of form the single phase of CuO. Structural, morphological, and electrical properties of copper oxide were measured with x-ray diffraction, Raman spectroscopy, scanning electron microscopy (SEM), and Hall effect techniques, respectively. Oxidation at temperatures lower than 200 °C showed that a thin layer of copper oxide, mainly of cuprous oxide (Cu2O), is grown on the surface of Cu. Oxidation at 300 °C promoted growth of a passivating oxide layer composed by CuO and Cu2O, even when Cu is oxidized during 24 h. In the range of temperatures from 400 to 700 °C, copper oxide layer was fragile and showed poor adherence to the Cu surface. Further Cu oxidation at higher temperatures promoted complete oxidation of the Cu sheets. However, the bulk was found to be composed by a mixture of Cu2O and CuO. Oxidation at 1000 °C for 24 h in flow of air or for 8 h in ambient of oxygen allowed formation of pure and high cristallinity CuO. Carrier concentration and mobility charge carriers of CuO estimated from Hall measurements for the CuO sample oxidized in oxygen atmosphere were found to be 7.64 × 1012 cm−3 and 1.1164 × 102 cm2 V−1 s−1, respectively.
The effect of the gaseous atmosphere in the growth of gallium arsenide (GaAs) films was studied. The films have been grown by close-spaced vapor transport (CSVT) technique in a home-made hot filament ...chemical vapor deposition (HFCVD) reactor using molecular hydrogen and molecular nitrogen as the transport agent. An important point about the gaseous atmosphere is the ease in creating volatile compounds when it makes contact with the GaAs source, this favors the transport of material in a CSVT system. Chemical reactions are proposed in order to understand the significant difference produced from the gaseous atmosphere. The films grown with hydrogen are (almost) continuous and have homogeneous layers with preferential orientation (111). The films grown with nitrogen are granular and rough layers with the coexistence of the orientations (111), (220) and (311) in the crystals. The incorporation of impurities in the films was corroborated by energy dispersive spectroscopy (EDS) showing traces of oxygen and nitrogen for the case of the samples obtained with nitrogen. Films grown in a hydrogen atmosphere show a higher band gap than those grown in a nitrogen atmosphere. With the results of XRD and micro-Raman we observe a displacement and broadening of the peaks, characteristic of a structural disorder. The calculations of the FWHM allow us to observe the crystallinity degree and determine an approximate crystallite size using the Scherrer’s equation.
Simulation and analysis of solar cells based on the heterojunction of zinc oxide doped with aluminum (AZO) and cadmium telluride (CdTe) with the structure (Al/AZO/CdTe/NiO/Ni) using the Simulator of ...the capacitance of solar cells - 1 dimension (SCAPS-1D) has been presented in this paper. AZO is used as a window layer and Nickel oxide (NiO) has been introduced as a hole transport layer (HTL). Through the software, the effect of thickness, absorber (CdTe), and window (AZO) layers carrier concentration, operating temperature, and resistances (series and shunt) have been studied. Simulation results show that the solar cell performance can be greatly improved by adjusting the layer's thickness and carrier concentration, obtaining optimal values of 10 nm and 1018cm−3 for the AZO layer, while for the CdTe layer they were 2 μm and 1015cm−3. The optimum series and shunt resistances are in the range of 1–3 Ωcm2 and 1800–2200 Ωcm2 respectively. A maximum power conversion efficiency (PCE) of 14.2% is achieved with an open circuit voltage (Voc) of 0.74 V, short circuit current density (Jsc) of 26.15 mA/cm2 and a fill factor (FF) of 72.83%, this shows AZO potential to be considered as an interesting material to replace CdS window layer.
This study explores the impact of hydrogen flow as a carrier gas on silicon oxycarbide thin films produced via hot wire chemical vapor deposition (HWCVD) using tetraethyl orthosilicate as a ...precursor. Systematically varying the hydrogen flow rates, the influence on thin film composition, microstructure, and optical properties is investigated. Employing diverse characterization techniques, such as X‐ray diffraction, field‐emission scanning electron microscopy (FE‐SEM), energy‐dispersive X‐ray spectroscopy, Fourier‐transform infrared (FTIR), X‐ray photoelectron spectroscopy (XPS), ellipsometry, and photoluminescence (PL) spectroscopy, it is revealed that there is a correlation between hydrogen flow rate and thin film elemental composition. Higher hydrogen flow rates result in increased silicon content and reduced contributions of oxygen and carbon. FE‐SEM images show agglomerates with improved homogeneity at higher flow rates. FTIR spectra highlight distinctive vibrational modes, including Si–H bonds. XPS confirms the emergence of Si–H bonds at elevated hydrogen flow rates. Ellipsometry indicates increased thickness and refractive index. PL spectra exhibit a broadband across the visible spectrum, influenced by hydrogen‐related defects and electronic transitions. This study provides findings for optimizing HWCVD parameters to tailor thin films for specific applications, emphasizing the important role of hydrogen flow as a carrier gas.
In this work, the effect of thermal annealing in H2 atmosphere on the photoluminescence (PL) of SiC x O y films is presented. These films were deposited by HFCVD technique at 800° C with 15.6 sccm of ...H2 flow. After deposition, the samples were annealed at temperatures between 640 and 970° C. After this process, the films were characterized by photoluminescence (PL), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM). An increases of PL intensity was observed for annealed sample at 640° C respect to the as deposited sample, although this intensity decreases when the annealing temperature increase to 970° C. The PL response is associated with the radiative defects such as Si-related oxygen deficiency center (Si-ODCs), Si-related oxygen vacancies (Si-NOVs), and non-bridging oxygen hole centers (NBOHCs). The PL behavior could be associated to the increases of radiative defects at 640°C like Si-NOVs and Si-ODCs while at higher temperature there is a decrease of these radiative defect. This PL behavior agrees with the structural change that was correlated with the XPS and FTIR results, specifically the Si-O, Si-O-Si, Si-H, Si-C-H bonds. Also, it was found by AFM that the roughness decreases when the annealing temperature increase due to a network rearrangement process promoted by the temperature and H 2 atmosphere. Finally, we can conclude that the luminescent of SiC x O y films could be improved with the use of a specific annealing temperature.
In this paper, a solar cell based on WOsub.3/CdTe heterojunction was analyzed and optimized, for which the following structure of the Al/AZO/WOsub.3/CdTe/NiO/Ni device was proposed, which was ...numerically simulated by the SCAPS 1-D software. Using the software, the effect of the thickness and carrier concentration of the absorber layer (CdTe) and the window layer (WOsub.3) was analyzed, and the optimal value of these parameters was found to be 2 µm and 10sup.15cmsup.−3 for the CdTe layer and 10 nm and 10sup.19cmsup.−3 for the WOsub.3 layer, respectively. The influence of the defect density of the WOsub.3/CdTe interface on the performance of the proposed cell was also analyzed, simulating from 10sup.10 to 10sup.16 cmsup.−2, obtaining better device performance at lower interface defect density. Another parameter analyzed was the operating temperature on the photovoltaic performance of the device, observing that the solar cell has a better performance at lower temperatures. Finally, a maximum optimized PCE of 19.87% is obtained with a Voc = 0.85 V, Jsc = 28.45 mA/cmsup.2, and FF = 82.03%, which makes the WOsub.3/CdTe heterojunction an interesting alternative for the development of CdTe-based solar cells.
In this paper, a solar cell based on WO3/CdTe heterojunction was analyzed and optimized, for which the following structure of the Al/AZO/WO3/CdTe/NiO/Ni device was proposed, which was numerically ...simulated by the SCAPS 1-D software. Using the software, the effect of the thickness and carrier concentration of the absorber layer (CdTe) and the window layer (WO3) was analyzed, and the optimal value of these parameters was found to be 2 µm and 1015 cm−3 for the CdTe layer and 10 nm and 1019 cm−3 for the WO3 layer, respectively. The influence of the defect density of the WO3/CdTe interface on the performance of the proposed cell was also analyzed, simulating from 1010 to 1016 cm−2, obtaining better device performance at lower interface defect density. Another parameter analyzed was the operating temperature on the photovoltaic performance of the device, observing that the solar cell has a better performance at lower temperatures. Finally, a maximum optimized PCE of 19.87% is obtained with a Voc = 0.85 V, Jsc = 28.45 mA/cm2, and FF = 82.03%, which makes the WO3/CdTe heterojunction an interesting alternative for the development of CdTe-based solar cells.
Nowadays, study of silicon-based visible light-emitting devices has increased due to large-scale microelectronic integration. Since then different physical and chemical processes have been performed ...to convert bulk silicon (Si) into a light-emitting material. From discovery of Photoluminescence (PL) in porous Silicon by Canham, a new field of research was opened in optical properties of the Si nanocrystals (Si-NCs) embedded in a dielectric matrix, such as SRO (silicon-rich oxide) and SRN (silicon-rich nitride). In this respect, SRO films obtained by sputtering technique have proved to be an option for light-emitting capacitors (LECs). For the synthesis of SRO films, growth parameters should be considered; Si-excess, growth temperature and annealing temperature. Such parameters affect generation of radiative defects, distribution of Si-NCs and luminescent properties. In this chapter, we report synthesis, structural and luminescent properties of SRO monolayers and SRO/SiO2 multilayers (MLs) obtained by sputtering technique modifying Si-excess, thickness and thermal treatments.
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