Increasing Deposition Temperature Research Articles

ОПТИЧЕСКИЕ И ЭЛЕКТРИЧЕСКИЕ СВОЙСТВА ВЕРТИКАЛЬНЫХ MoS2 НАНОСТРУКТУР

Ultrathin two-dimensional layered crystalline films of molybdenum disulfide have unique electrical properties and can be used in solar cells, photoelectric converters, thermoelectric and electrochromic devices. The highest quality thin films of molybdenum disulfide can only be obtained by thermally activated chemical vapor deposition. However, the nature of the influence of the conditions of formation of MoS2 films on their composition, structure, structure, and properties has not been systematically studied and remains unclear. In this regard, the task of establishing experimentally the main physicochemical regularities of the process of chemical deposition of MoS2 films from the gas phase becomes topical. This article describes the results of a study of the optical and electrical properties of vertical MoS2 nanostructures. Studies of absorption and reflection, photoluminescence, current-voltage characteristics, and the effect of temperature on resistance were carried out. We studied vertical nanopetals deposited at different temperatures (250°C, 550°C, and 750°C) and only one film with dendrites deposited at 350°C in the Mo(CO)6 - H2S system. Films deposited at 250°C, 550°C, and 750°C consist of vertical nanoparticles. The dimensions, thickness, and distance between them increase with increasing deposition temperature; a decrease in the deposition temperature reduces the size of the nanopetals. The film deposited at 350°C has a dendritic structure (vertical branched sheets). The obtained results of studying the properties of films show that their optical properties significantly depend not only on the size of the nanostructural elements that form the film, but also on their morphology. Films formed by both vertical nanoleaves and dendrites have unique electrophysical properties, demonstrating quantum conductivity represented by charge density waves. The discovered unique electrophysical properties are of great interest for modern optoelectronics.

Crystal-phase-specific near-infrared photoluminescence from Er3+-doped Bi2O3 thin films

Er3+-doped Bi2O3 films were sputter deposited on Si(100) substrates at room temperature with H2O vapor as an oxygen source gas. Crystal phases appearing after postannealing in an O2 atmosphere included single-phases of α-Bi2O3, γ-Bi2O3, and δ-Bi2O3, as well as a mixed phase of α-Bi2O3 and γ-Bi2O3. Selection of the crystal phase was possible in terms of H2O pressure and postannealing temperature. Photoluminescence spectra from Er3+ ions excited at a laser wavelength of 532 nm revealed distinct spectral features specific to the crystal phases. A clear crystal-field splitting feature consisting of eight emission lines was observed in PL spectra from sufficiently oxidized α-Bi2O3:Er films, indicating that Er3+ ions occupied low-symmetry C2v sites of Bi3+. The optimum annealing temperature for optical activation of Er3+ ions was between 400 and 450 °C. The emission intensity of α-Bi2O3:Er deposited with H2O was seven times higher than that of α-Bi2O3:Er deposited with O2 probably because larger numbers of Er3+ could substitute Bi3+ sites under reduced condition. Increasing deposition temperature lowered the emission intensity due to the loss of OH and H species from the as-deposited films. The emission spectra of γ-Bi2O3:Er were featureless and its emission intensity was one order of magnitude lower than that of α-Bi2O3:Er. The low-temperature phase of δ-Bi2O3:Er turned out to be entirely emission inactive. Reactions at the interface between the Bi2O3 film and the Si substrate were promoted upon postannealing at 500 °C. The resulting Bi2SiO5:Er exhibited a weak emission spectrum with four emission lines, which reflected occupation at tetragonal Bi3+ sites in the (Bi2O2)2− layers.

Effects of deposition temperature on structure, residual stress and corrosion behavior of Cr/TiN/Ti/TiN films

Composite TiN film was prepared on AZ31 at four sets of different deposition temperatures. X-ray diffraction and X-ray fluorescent were employed to determine the structure, residual stress, thickness and chemical elements. A scratch tester with Rockwell C diamond styli and electrochemical workstation were used to evaluate the adhesion and corrosion behavior of the obtained film. The effects of deposition temperature on structure, residual stress, adhesion, thickness and corrosion behavior were investigated as well. The results show that the films are composed of TiN with (111), (200) and (222) planes, Ti with (002) plane, and Cr (110) plane. The maximum residual compressive stress is about 413.4 MPa, and the elements distribution is not uniform when the film deposited at 150 °C. With the increase of deposition temperature, the grain size and crystallinity increase, the thickness decreases, the residual stress decreases first and then increases, the film becomes more compact and has better corrosion resistance. However, when the deposition temperature is greater than 250 °C, the surface roughness and the thermal stress begin to increase, the bonding performance and the corrosion resistance also decrease.

Investigation on the structural properties and correlation of the optical constants of Cd1-xZnxS thin films with bath deposition temperature

Cd1-xZnxS thin films were deposited by chemical bath deposition (CBD) technique, which is simple and cost effective, in a chemical bath containing appropriate amount of cadmium acetate, zinc acetate, and thiourea as precursors, in a clean glass substrate. The deposition was carried out by varying the bath temperatures (70 °C, 75 °C, 80 °C, and 85 °C) of the precursor solution. The XRD results indicate the existence of hexagonal structures of Cd1-xZnxS with an average crystallite size of ∼ 27–41 nm. EDX studies confirm the presence of Cd, Zn, and S in the films. HRTEM and SAED patterns show the crystalline nature of the films with the coexistence of the hexagonal phase. The optical constants viz; optical band gap, Urbach energy, static refractive index, and optical conductivity were studied by using UV- Vis transmission spectra as a function of CBD temperature. It was observed that with the increase of bath temperature in the above range, there were concomitant decreases in optical band gap from ∼3.3 to 2.8 eV. The Urbach energy, optical conductivity, and static refractive index of the films increase with the increase in bath deposition temperature. FTIR studies confirm the formation of ternary Cd1-xZnxS thin films.

Residual Oxygen Effects on the Properties of MoS2 Thin Films Deposited at Different Temperatures by Magnetron Sputtering

Molybdenum disulfide (MoS2) thin films were deposited at different temperatures (150 °C, 225 °C, 300 °C, 375 °C, and 450 °C) on quartz glass substrates and silicon substrates using the RF magnetron sputtering method. The influence of deposition temperature on the structural, optical, electrical properties and deposition rate of the obtained thin films was investigated by X-ray diffraction (XRD), Energy Dispersive Spectrometer (EDS), Raman, absorption and transmission spectroscopies, a resistivity-measuring instrument with the four-probe method, and a step profiler. It was found that the MoS2 thin films deposited at the temperatures of 150 °C, 225 °C, and 300 °C were of polycrystalline with a (101) preferred orientation. With increasing deposition temperatures from 150 °C to 300 °C, the crystallization quality of the MoS2 thin films was improved, the Raman vibrational modes were strengthened, the deposition rate decreased, and the optical transmission and bandgap increased. When the deposition temperature increased to above 375 °C, the molecular atoms were partially combined with oxygen atoms to form MoO3 thin film, which caused significant changes in the structural, optical, and electrical properties of the obtained thin films. Therefore, it was necessary to control the deposition temperature and reduce the contamination of oxygen atoms throughout the magnetron sputtering process.

Diffusion processes in germanium and silicon films grown on Si3N4 substrates

In this article, the results of investigation of processes occurring during the molecular-beam deposition of germanium layers on Si$_3$N$_4$ dielectric substrates within a wide range of the Ge film growth temperatures (30 to 600{\deg}C) are presented. The intensity of the IR absorption bands related to the vibrations of the N$-$H and Si$-$N bonds are established to decrease with the increase of the Ge deposition temperature. It appears that this phenomenon cannot be explained only as a thermally activated process. Simultaneously, the peak corresponding to the Ge$-$N vibration bonds emerges in the X-ray photoelectron spectra. We suppose that the deposition of germanium layers on Si3N4 dielectric substrates containing hydrogen atoms causes the diffusion of hydrogen atoms from the dielectric layer into the growing film. The experimental results may be interpreted in terms of a model, according to which the migration of hydrogen atoms from the Si$_3$N$_4$ layer into the growing germanium film is due to the difference in chemical potentials of hydrogen atoms in the dielectric layer and the germanium film. This process initiates the diffusion of germanium atoms in the opposite direction, into the Si$_3$N$_4$ layer, where they connect to free bonds of nitrogen atoms arising due to the escape of hydrogen atoms. The analogous processes occur during the deposition of silicon layers on Si$_3$N$_4$ substrates.

Effect of deposition temperature on phase composition, morphology and mechanical properties of plasma-sprayed Yb2Si2O7 coating

Phase composition, microstructure and mechanical properties of ytterbium disilicate (Yb2Si2O7, YbDS) coatings fabricated via atmospheric plasma spray (APS) at different deposition temperatures were studied. Two layers with distinct pore distributions were observed in the YbDS top coat, the formation of pores correlated fairly well with the thermal gradients of splats after the droplets impinged on the substrate or deposited splats. Microstructure evolution with the thicknesses of YbDS top coat resulted from splat stacking and temperature accumulation. In addition, the significant crystallinity improvement and cracks reduction of YbDS top coat arose with the increased deposition temperature. X-ray diffraction patterns indicated that the metastable ytterbium monosilicate (Yb2SiO5, YbMS) appeared in YbDS coatings and they disappeared after thermal-treatment due to the phase transformation. The mechanical properties of the YbDS coatings were affected notably by the phase composition and microstructure.

Regulation of absorption coefficients between multi-photon and free-carrier in PbTe films by deposition temperature

We investigate the effects of deposition temperature on a crystal structure and electrical and optical properties of PbTe thin films sputtered on BaF2 (111). We observe that with the increase in deposition temperature, the grain size increases, and when it reaches 300 °C, the grain size reaches the maximum, and the preferred orientation begins to change. At 400 °C, the lattice mismatch rate decreases from 4.2% to 3.6% due to lattice contraction caused by reevaporation, and the conduction type changes from p-type dominated by a mismatch strain defect to n-type dominated by a Te vacancy. These changes lead to the interplay of various absorption mechanisms. We find that, in addition to the overall absorption coefficient curve significantly changing with deposition temperature, more importantly, the contribution of various internal absorption mechanisms to the below bandgap absorption spectrum does no longer synchronize. Instead, the contribution of an acoustic phonon to free-carrier absorption (FCA) decreases, while the relative contribution of optical phonon, impurity, two-photon absorption (2PA), and three-photon absorption (3PA) increases. This regulation effect reaches its maximum at 300 °C, which of various absorption mechanisms at 300 °C are 6.3, 11.6, 4.4, and 14.7 times higher than that at 20 °C corresponding to an optical phonon, impurity, 2PA, and 3PA processes, respectively. These results indicate that it should be possible to regulate the FCA, 2PA, and 3PA processes by changing the deposition temperature, thus making them suitable for applications in optoelectronic devices.

Low-temperature growth of crystalline Tin(II) monosulfide thin films by atomic layer deposition using a liquid divalent tin precursor

In this study, better-quality stoichiometric SnS thin films were prepared by atomic layer deposition (ALD) using a liquid divalent Sn precursor, N, N′-di-t-butyl-2-methylpropane-1,2-diamido tin(II) [Sn(dmpa)], and H2S. A relatively high growth per ALD cycle (GPC) value of approximately 0.13 nm/cycle was achieved at 125 °C. Furthermore, crystalline SnS films could be grown from room temperature (25 °C) to a high temperature of 250 °C. Density functional theory (DFT) calculations were used to examine the surface reactions and self-limiting nature of the Sn precursor. Mixed phases of cubic (π) and orthorhombic (o) SnS films were deposited at low temperatures (25–100 °C), whereas only the orthorhombic phase prevailed at high growth temperatures (>125 °C) based on the complementary results of X-ray diffractometry (XRD), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS) analyses. The optoelectronic properties of the SnS films were further evaluated by spectroscopic ellipsometry (SE) analysis. The results from the SE analysis supported the observed change from mixed π-SnS and o-SnS to o-SnS with increasing deposition temperature and allowed the determination of the energy bandgap (~1.1 eV) and a relatively broad semi-transparent window (up to 3000 nm). Overall, this new ALD process for obtaining a good quality SnS is applicable even at room temperature (25 °C), and we foresee that this process could be of considerable interest for emerging applications.

Role of TiO2 coating layer on the performance of Cu2O photocathode in photoelectrochemical CO2 reduction

TiO2 is usually employed as a protective layer for Cu2O in photoelectrocatalytic CO2 reduction. However, the role of TiO2 layer on CO2 reduction activity and selectivity is still elusive. In this work, a systematic investigation is carried out to probe the impact of the deposition parameters of TiO2 overlayer, including the temperature and thickness, on CO2 reduction performance. Compositional and (photo-)electrochemical analysis is performed to explore the property of TiO2 overlayers. Carrier behavior, including donor density and electron energy, and stability of TiO2 are demonstrated to be influenced by atomic layer deposition conditions and thus play a role in controlling CO2 reduction reaction. Specifically, as the thickness of the TiO2 layer increases from 2 to 50 nm, the electron energy tends to be lowered accompanying the electron transfer mode from tunneling for TiO2 thin layers to type II for thick TiO2, leading to a decrease in CO2 reduction selectivity. With an increase of the TiO2 deposition temperature, the stability increases with a loss of conductivity. Cu2O coated with 2 nm TiO2 at 150 °C is proven to be the optimized candidate in this work for photoelectrochemical reduction of CO2 to CO, HCOOH and CH3COOH under an applied bias of −0.4 versus RHE.

Ellipsometry Study of CdSe Thin Films Deposited by PLD on ITO Coated Glass Substrates.

Cadmium selenide (CdSe) thin films were deposited on indium tin oxide (ITO) coated glass substrates using pulsed laser deposition (PLD) technique under different growth temperatures. Samples were investigated for their structural, morphological, and optical properties through X-ray diffraction (XRD), atomic force microscopy (AFM), and UV-Vis-NIR spectroscopy. AFM analysis revealed that the surface roughness of the as-grown CdSe thin films increased with the increase in deposition temperature. The optical constants and film thickness were obtained from spectroscopic ellipsometry analysis and are discussed in detail. The optical band gap of the as-grown CdSe thin films, calculated from the Tauc plot analysis, matched with the ellipsometry measurements, with a band gap of ~1.71 eV for a growth temperature range of 150 °C to 400 °C. The CdSe thin films were found to have a refractive index of ~3.0 and extinction coefficient of ~1.0, making it a suitable candidate for photovoltaics.

DEPOSITION OF TRANSPARENT CONDUCTIVITY OF FLUORINE-DOPED SnO2 THIN FILMS BY SPRAY PYROLYSIS METHOD

SnO2 and SnO2:F thin films were successfully deposited on a glass wafer substrate by spray pyrolysis method using SnCl2.5H2O and NH4F as precursors. The effect of deposition temperature and fluorine concentration on the crystal phase formation of SnO2 was investigated by XRD. The results showed that the films were crystallized in the form of SnO2 with a tetragonal structure at deposition temperature above 400 oC. No XRD peaks related to SnO2 were found on the films that deposited at a temperature lower than 350 oC. The sheet resistance of the SnO2 films was increased with the increase in the deposition temperature. The crystalline structure of the SnO2 films did not change in the presence of fluorine impurities while their sheet resistance was significantly decreased. The minimum sheet resistance was 3.7 (Ω\□) corresponding to the samples deposited with the fluorine concentration of 20 wt%. SEM images also showed the crystal shape of SnO2 in which crystal size decreases with an increase in fluorine concentration. Both SnO2 and SnO2:F exhibited good transparent properties in visible light. The bandgap of the SnO2 films was about 3.90 eV and was slightly expanded when the concentration of fluorine was increased.

Effect of Deposition and Annealing Temperatures on Physical Properties of CdSe Nanoparticles Thin Film for Solar Cell Applications.

High quality nanoparticles Cadmium Selenide, CdSe, thin films were prepared by Chemical Bath Deposition (CBD) technique. The films were deposited on glass substrate at different bath temperatures, using cadmium chloride as 〖Cd〗^(+2) ion source and sodium selenosulphite as 〖 Se〗^(-2) ion source. The pH of the bath was kept constant around 11 ± 0.1. The air annealed film at different temperatures for 1h was included in this work. The effect of chemical bath temperatures and annealing in air on structure and optical properties were studied. The structural properties were studied by X-ray diffraction for all thin films and revealed a Polycrystalline nature with cubic structure having preferential orientation along (111) plane direction. The calculated crystallite size was found to be between 4.902 nm and 7.937 nm, and this indicates that all the prepared CdSe thin films are nanoparticles. It has been found that crystallite size increases with increasing deposition temperature and annealing temperature. Optical properties were studied by UV-vis spectrophotometer for all films, which shows blue shift in the peak. The values of the energy gap (allowed direct transitions) calculated from the absorption spectra, were between 2.2 and 3 eV, in contrast to the bulk, energy gap which is 1.74 eV. The temperature dependence of electrical resistivity of CdSe nanoparticles (at powder form) measured in the temperature range of 300- 455 K. The electrical measurement results show that the electrical resistivity of the samples decreases with temperature down to 4.5×〖10〗^5 Ω cm at 455 K.

Effect of deposition temperature on the properties of F and Ti co-doped zinc oxide films

ZnO + 1.5 wt.% TiO2 powder is calcined at [Formula: see text] and sintered at [Formula: see text] to prepare the Ti-doped ZnO ceramic target, and RF sputtering is used to deposit F and Ti co-doped ZnO (FTZO) films by introducing Ar + CF4 mixing gas (CF4 flow rate is 0.2%) into the deposition chamber. The deposition temperature is changed from room temperature to [Formula: see text], and the thicknesses of all deposited FTZO films are controlled at about 320 nm. After FTZO films are deposited, X-ray diffraction pattern is used to analyze their crystalline properties, field-effect scanning electron microscope is used to observe their surface morphologies and confirm their thicknesses. n&k analyzer is used to measure the transmittance spectra in the wavelength range of 300–1100 nm and we find that the absorption edge of FTZO films is shifted to lower wavelength as the deposition temperature increases. The optical energy band gap of FTZO films is calculated using the transmittance spectra and the electrical properties of FTZO films are measured using a Hall equipment. Finally, secondary-ion mass spectrometry is used to analyze the C, O, F, Si and Ti elements with different deposition temperatures for confirming the existence and distribution of [Formula: see text] ions and non-existence of C element.

Inherently Area-Selective Atomic Layer Deposition of Manganese Oxide through Electronegativity-Induced Adsorption.

Manganese oxide (MnOx) shows great potential in the areas of nano-electronics, magnetic devices and so on. Since the characteristics of precise thickness control at the atomic level and self-align lateral patterning, area-selective deposition (ASD) of the MnOx films can be used in some key steps of nanomanufacturing. In this work, MnOx films are deposited on Pt, Cu and SiO2 substrates using Mn(EtCp)2 and H2O over a temperature range of 80–215 °C. Inherently area-selective atomic layer deposition (ALD) of MnOx is successfully achieved on metal/SiO2 patterns. The selectivity improves with increasing deposition temperature within the ALD window. Moreover, it is demonstrated that with the decrease of electronegativity differences between M (M = Si, Cu and Pt) and O, the chemisorption energy barrier decreases, which affects the initial nucleation rate. The inherent ASD aroused by the electronegativity differences shows a possible method for further development and prediction of ASD processes.

Hydrogen density-of-states distribution in β-Ga2O3

Hydrogen bonding in β-Ga2O2 is investigated using hydrogen effusion measurements. The samples were grown by plasma-assisted pulsed laser deposition. With increasing deposition temperature, the total H concentration decreases from 8.1 × 1019 to 9.2 × 1018 cm−3. The dependence of the hydrogen chemical potential, μH, on the H concentration is derived from the effusion spectra and subsequently used to determine the H density-of-states distribution. β-Ga2O2 deposited at Tdep ≤ 723 K exhibits a needle-like peak in the H density-of-states distribution at ≈1.8 eV below the H transport states. With increasing Tdep, the H density-of-states changes and two broad peaks emerge that are located at ≈1.7 and 2.4 eV below the H transport states for Tdep ≥ 873 K.

Synthesis and Theoretical Concepts of Boron Nitride Nanowires Grown on Nitrides Stainless Steel Surface by Hybrid Gas Phase Process

Synthesize of Boron Nitride nanowires were made by utilizing Austenitic hardened steel AISI 316 with a nitriding layer of 15–16 μm thickness. Deposition experiments at deferent substrate temperatures for BN Nanowires productions were carried out with the help of a blended gas stage depositing handle procedure (PVD and CVD). Chemical composition and crystallinity along with the average grain size for BN phases was investigated by using XRD test and FTIR spectrum. The SEM images was used to examine the surface topography. Finally theoretical investigations computations were performed by thickness useful hypothesis (DFT) in Gaussian 09 bundle. According to our results, the impact of the depositing temperature on the chemical composition and the structure should be pointed out as the major effect for the higher deposition rate that leads to thicker and more dense BN surface film, where the more uniform BN Nanostructures wires with a regular diameter of 20 nm and average grain size of ~18nm was compelled through novel materializing crystalline stages causing grain size to rise with increasing deposition temperature to specific level.

Influence of temperature and nickel catalyst on the structural and optical properties of indium oxide nanostructured films synthesized by chemical vapor deposition technique

This work reports the synthesis of indium oxide pyramids, octahedrons, and faceted nanostructures on silicon and nickel-coated silicon substrates via carbothermal reduction of In2O3 powder assisted by a 1% hydrogen/balance nitrogen mixed gas as forming and carrier gas. The influence of deposition temperature on the morphology, structural, and optical properties of the produced films was investigated by varying the source temperature from 850 to 1000 °C. Characterization of the In2O3 nanostructures was performed using FESEM, EDX, XRD, and UV–vis spectrophotometry. Material growth, film thickness, crystallites size, and crystallinity were observed to be enhanced with increased deposition temperature. The use of Ni as a catalyst resulted in the production of high yield films even at the low growth temperature. XRD revealed polycrystalline films with preferential growth in the (222) plane. Films synthesized on Si substrate showed more regular reflection as compared to those grown on Ni/Si. The optical band gap was found to decrease from 3.4 to 2.89 eV with increased deposition temperature. Bandgap narrowing was attributed to the increase in grain size and film thickness.

Structural and mechanical properties of nanocrystalline Ga2O3 films made by pulsed laser deposition onto transparent quartz substrates

This work reports on the correlation between structure, surface/interface morphology and mechanical properties of pulsed laser deposited (PLD) β-Ga2O3 films on transparent quartz substrates. By varying the deposition temperature in the range of 25 °C–700 °C, ∼200 nm thick Ga2O3 films with variable microstructure and amorphous-to-nanocrystalline nature were produced onto quartz substrates by PLD. The Ga2O3 films deposited at room temperature were amorphous; nanocrystalline Ga2O3 films were realized at 700 °C. The interface microstructure is characterized with a typical nano-columnar morphology while the surface exhibits the uniform granular morphology. Corroborating with structure and surface/interface morphology, and with increasing deposition temperature, tunable mechanical properties were seen in PLD Ga2O3 films. At 700 °C, for nanocrystalline Ga2O3 films, the dense grain packing reduces the elastic modulus Er while improving the hardness. The improved crystallinity at elevated temperatures coupled with nanocrystallinity, the β-phase stabilization is accounted for the observed enhancement in the mechanical properties of PLD Ga2O3 films. The structure-morphology-mechanical property correlation in nanocrystalline PLD β-Ga2O3 films deposited on quartz substrates is discussed in detail.

Growth temperature-dependent morphological, optical, and electrical study of SnO2 thin film by atomic layer deposition

Low temperature, high quality SnO2 thin film successfully deposited by the atomic layer deposition (ALD) method using tetrakis (dimethylamino)Sn (TDMASn) and O3-plasma. The influence of various growth temperatures having ranges between 115 °C to 250 °C on the film growth rate, morphology, composition, optical and electrical properties have been elucidated, and remarkable differences were noticed for possible electron transport layer (ETL). It was worth observing that the film growth rate steeply increased from 0.046 nm/cycle to 0.192 nm/cycle between the growth temperature range 115–250 °C because of the rapid dissociation of TDMASn precursor relative to temperature increase. The optical transmittances of films showed 81%–97% at the visible region for all growth temperatures; however, the optical bandgap energy of the SnO2 film was decreased from 3.4 eV to 3.1 eV while increasing deposition temperature. During lower deposition temperature of 115 °C, the film obtained high resistivity (7.3 × 102 Ω cm), while at a high growth temperature of 200 °C almost impurity-free low resistivity (8.9 × 10−4 Ω cm) film can be achieved apart from high carrier concentration (1.4 × 1021 cm−3) and 12.5 cm2 V−1s−1 mobility.