Increasing Substrate Temperature Research Articles

Highly Selective Dimethylamine Sensing Performance of TiO₂ Thin Films at Room Temperature.

To date, reports on metal oxide semiconductors for selective detection of dimethylamine (DMA) is in scarce. Hence in our study, we report titanium oxide (TiO₂) as a promising candidate for tuned selectivity towards DMA. Highly uniform TiO₂ thin films were successfully deposited on glass substrates using reactive dc magnetron sputtering at various substrate temperatures. Polycrystalline nature of rutile TiO₂ was confirmed by X-ray diffraction technique (XRD). The uniform surface morphology of the sputtered TiO₂ thin films was revealed by Field Emission Scanning Electron Microscopy (FESEM). An upsurge in optical band gap from 3.18 to 3.4 eV was observed with increase in substrate temperature. The sensing studies of the sputtered TiO₂ thin films exhibited a significant sensor response towards the lower concentration of DMA at ambient temperature. It is deemed that this work will provide an insight to develop DMA sensors based on TiO₂ thin films.

Structural, Morphological, and Optical Properties of Iron Doped WO3 Thin Film Prepared by Pulsed Laser Deposition

The iron doped tungsten-oxide (Fe and WO3) thin film with different morphology and crystalline structures were obtained for different substrate temperatures at the oxygen pressure of 14.66 Pa. The Fe-doped WO3 films were deposited by pulsed laser deposition (PLD). The influence of the substrate temperature on the surface and on the crystalline phases of the films was studied. The XRD (X-ray diffraction) analysis indicates the changing in the crystalline phases from γ-monoclinic to a mixture of γ-monoclinic and hexagonal phases dependent on the temperature of annealing and as-grown films. Related to the as-grown and annealing films conditions, the SEM (scanning electron microscopy) shows a change in the image surface from nanoneedles, to nanoporous, and further to long nanowires and broad nanobands. Energy-dispersive X-ray spectroscopy (EDX) shows the elemental composition of the Fe-doped WO3 film as-grown and after annealing treatment. Raman spectroscopy presented the main vibration mode of the Fe-doped WO3 thin film. The optical energy bandgap of the films is decreasing as the substrate temperature increases.

Fabrication of Illumination-Dependent Cu/p-Si Schottky Barrier Diodes by Sandwiching MoO3 Nanoplates as an Interfacial Layer via JNSP Technique

Highly oriented ultrathin MoO3 nanoplate thin films have been synthesized on a large scale using a low-cost spray pyrolysis technique at different substrate temperatures (350°C, 400°C, 450°C, and 500°C). High-quality single-phase orthorhombic α-MoO3 nanoplate film was observed by x-ray diffraction analysis. The surface morphology of the coated films was analyzed by field-emission scanning electron microscopy, revealing two different surface structures, viz. nanorods and nanoplates. Under atomic force microscopy, the surface roughness of the films was found to decrease with increasing substrate temperature. The optical properties of the α-MoO3 nanoplate thin films were analyzed by ultraviolet–visible and photoluminescence spectroscopy. The optical bandgap varied from 2.8 eV to 3.2 eV, recording a red-shift in the emission, with increasing substrate temperature from 350°C to 500°C. The electrical conductivity was also found to increase linearly with increasing substrate temperature. Various photodiode parameters such as ideality factor (n), barrier hight (ФB), photo sensitivity (PS), resistivity (R), quantum efficiency (QE) and detectivity (D*) were calculated for different light intensities from 0 mW/cm2 to 120 mW/cm2 based on the I–V characteristic. The diode fabricated at 500°C showed a remarkably high photosensitivity and specific detectivity of 610.51% and 1.149 × 1011 Jones when measured at 120 mW/cm2.

Effect of synthesis temperature on the phase formation of NiTiAlFeCr compositionally complex alloy thin films

The synthesis temperature dependent phase formation of Ni10Ti10Al25Fe35Cr20 thin films is compared to a bulk processed sample of identical composition. The as-cast alloy exhibits a dual-phase microstructure which is composed of a disordered BCC phase and AlNiTi-based B2- and/or L21-ordered phase(s). Formation of the BCC phase as well as an ordered AlNi-based B2 phase is observed for a thin film synthesised at 500 °C (ratio of synthesis temperature of thin film to melting temperature of bulk alloy: T/Tm = 0.49), which is attributed to both surface and bulk diffusion mediated growth. Post deposition annealing at 900 °C (T/Tm = 0.75) of a thin film deposited without intentional heating results in the formation of NiAlTi-based B2 and/or L21-phase(s) similar to the bulk sample, which is attributed to bulk diffusion. Depositions conducted at room temperature without intentional substrate heating (T/Tm = 0.20) resulted in the formation of an X-ray amorphous phase, while a substrate temperature increase to 175 °C (T/Tm = 0.28) causes the formation of a BCC phase. Atom probe tomography of the thin films deposited without intentional substrate heating and at 175 °C indicates the formation of ∼5 nm and ∼10 nm FeAl-rich domains, respectively. This can be rationalized based on the activation energy for surface diffusion, as Ti and Ni exhibt 2.5 to 4 times larger activation energy barriers than Al, Fe and Cr. It is evident from the homologous temperature that the phase formation observed at 500 °C (T/Tm = 0.49) is a result of both surface and bulk diffusion. As the temperature is reduced, the formation of FeAl-rich domains can be understood based on the differences in activation energy for surface diffusion and is consistent with kinetically limited thin film growth.

The effect of substrate temperature and Sn/Se mass ratio on the co-evaporated SnSe thin film for photovoltaic application

In this work, SnSe thin films were prepared by co-evaporation method with different Sn/Se mass ratio and substrate temperature. The composition, structure, morphology and optical properties of the film were researched. The characterized results show that the film has a relatively pure SnSe phase under Sn/Se mass ratio of 1.50, and the crystallinity of SnSe thin films increases with the increase of substrate temperature. All the films showed p-type conductivity with a minimum resistivity of 1.96 × 10−2 Ωcm and maximum electron mobility of 24.8 cm2V−1s−1. Finally, SnSe solar cells with a device structure of soda-lime glass/Mo/SnSe/CdS/i-ZnO/ITO/Ni/Al were fabricated and a best power conversation efficiency of 0.89% was achieved at the optimum substrate temperature and Sn/Se mass ratio. These results guide high quality SnSe thin films growth and contribute to the development of efficient SnSe solar cell by using evaporation based method.

Structural, morphological and magnetic properties of GaSbMn/Si(111) thin films prepared by radio frequency magnetron sputtering

The structural, chemical and magnetic properties of GaSbMn thin films grown by Radio Frequency magnetron sputtering on Si (111) substrates, varying the growth temperature, were studied. X-ray diffraction analysis shows that the samples are polycrystalline with multiple phases, and their crystalline quality improves as the substrate temperature increases. A morphological study was carried out using transmission electron microscopy and scanning electron microscopy, revealing the formation of magnetic nanoparticles and precipitates, which depends on the growth temperature. The electronic structure of the films, studied by X-Ray Photoelectron Spectroscopy, exhibits a closely spaced doublet that arises from the spin-orbital coupling into Ga 2p, Sb 3d, and Mn 2p spectra. Measurements of Magnetization as function of temperature, performed in a low external magnetic field (0.05 T), revealed a ferromagnetic ordering from low temperatures to above room temperature, due to the existence of the multiphases GaSbMn, MnSb and GaMn. The magnetization loops taken at 5 K, 150 K, 298 K and 350 K, show that saturation magnetization depends on the sample preparation temperature. For the sample grown at 573.15 K, saturation magnetization decreases with increasing temperature from 5 to 350 K, while for the sample grown at 773.15 K, it is almost independent of temperature, due to the formation of MnSb and GaMn precipitates embedded into GaSb semiconductor matrix.

Anisotropy of additively manufactured AlSi10Mg: threads and surface integrity

Implementing additive manufacturing in an industry, particularly for critical applications of lightweight aluminum (AlSi10Mg), requires part properties that are both accurate and precise to conform to the intent of a robust design. In this experimental study, the objective was to evaluate anisotropy in part properties (i.e., flatness, surface roughness, surface porosity, surface hardness, pre-hole shrinkage, drilling thrust force, and thread-stripping force) when the part orientation (i.e., print inclination and recoater angle) was independently changed. This study developed and investigated an innovative procedure for determining anisotropy in part properties. The part properties were evaluated by designing specific features on a tailor-made flat plate. The replicas of the aluminum plate were additively manufactured at varying orientations using two commercial EOS parameter sets for the laser-based powder bed fusion technique. Conventional measurement equipment was used to analyze all the part properties, except the thread-stripping force, which was measured using a custom-made setup. All the part properties indicated a considerable degree of anisotropy, excluding the drilling thrust force. The printing parameters dictate the significance of the anisotropy. The anisotropy in flatness and pre-hole shrinkage decreases with an increased substrate temperature and a decrease in energy input and thermal gradient. The presence of surface overlapping contours in the scan strategy and an increased energy input can reduce anisotropy in surface roughness and hardness. No significant anisotropy was detected when the recoater angle was changed. This study helps designers establish and substantiate design for additive manufacturing that is within the limits of appropriate anisotropy for a robust design.

Substrate temperature influenced ZrO2 films for MOS devices

The effect of substrate temperature on the direct current magnetron‐sputtered zirconium oxide (ZrO2) dielectric films was investigated. Stoichiometric of the ZrO2 thin films was obtained at an oxygen partial pressure of 4.0 × 10−2 Pa. X‐ray diffraction studies revealed that the crystallite size in the layer was increased from 4.8 to 16.1 nm with increase of substrate temperature from 303 to 673 K. Metal‐oxide‐semiconductor devices were fabricated on ZrO2/Si stacks with Al gate electrode. The dielectric properties of ZrO2 layer and interface quality at ZrO2/Si were significantly influenced by the substrate temperature. The dielectric constant increased from 15 to 25, and the leakage current density decreased from 0.12 × 10−7 to 0.64 × 10−9 A cm−2 with the increase of substrate temperature from 303 to 673 K.

Study of graphene layer growth on dielectric substrate in microwave plasma torch at atmospheric pressure

The initial stage of graphene layer deposition on silicon oxide substrate by ethanol decomposition in dual-channel microwave plasma torch at atmospheric pressure was studied in dependence on precursor flow rate and delivered microwave power. Depending on ethanol flow rate and substrate temperature, horizontally or vertically aligned graphene nanosheets with various density could be prepared directly on dielectric substrate. In the regime with high microwave power, above 400 W, mixture of amorphous carbon particles and graphene sheets was deposited on the substrate. Prepared layers were analyzed by scanning electron microscopy (SEM), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). The microwave plasma diagnostics was carried out using optical emission spectroscopy (OES). The sample analysis showed increasing density of horizontally aligned carbon nanosheets with increasing ethanol flow rate and their delamination and transition into vertically aligned graphene sheets with increasing substrate temperature. The Raman spectroscopy analysis of layers showed presence of D (1345 cm−1), G (1585 cm−1) and 2D (2685 cm−1) peaks with 2D/G ratio of 1.59 and full width at half maximum (FWHM) of 2D peak was 42 cm−1, corresponding to few layer graphene structure. In case of amorphous nanoparticles deposition, the D* peak at 1210 cm−1 and D** at 1500 sccm−1 was observed in Raman spectra with D/G ratio of 1.19 and C1s XPS spectra of carbon contained 20.4 at.% of sp3 carbon phase in comparison to 8.3 at.% in case of graphene nanosheets layer. High D/G ratio, up to 3.5, and low intensity 2D band was characteristic for vertically aligned graphene nanosheets layers. The possibility to influence density and size of graphene nanosheets on substrate represents promising alternative for future deposition of graphene on arbitrary substrate.

Semitransparent and conductive CaSi2 films for silicon device applications

The purpose of this work was to comparatively analyze the structural, optical and electrical properties of calcium silicides (CaSi, and CaSi2) on silicon in the form of epitaxial and nanocrystalline films grown on Si(001) and Si(111) substrates and to determine the field of use. An analysis of the structure of the grown films showed the presence of contributions from amorphous, nanocrystalline and crystalline phases (Ca2Si, CaSi and CaSi2) with an increase of the Si substrate temperature from 190 °C to 500 °C. It has been established that transparency in the photon energy range 0.2–1.3 eV in CaSi2 films is associated with a low density of states at the Fermi level, and high conductivity is determined by the concentration of free carriers up to 1021 cm–3 at T = 7–300 K. The latter provide high electrical conductivity up to 1200 (Ω cm)−1, low sheet resistance (26–40 Ω/square) and high reflection (80%–90%) at photon energies below 0.4 eV. The unique properties of CaSi2 films are promising for the creation of transparent conductive pads for silicon-based solar cells and the development of infrared photodiodes with a Schottky barrier on p-type silicon.

Zinc Oxide Films with High Transparency and Crystallinity Prepared by a Low Temperature Spatial Atomic Layer Deposition Process.

Zinc oxide (ZnO) attracts much attention owing to its remarkable electrical and optical properties for applications in optoelectronics. In this study, ZnO thin films were prepared by spatial atomic layer deposition with diethylzinc and water as precursors. The substrate temperature was varied from 55 to 135 °C to investigate the effects on the optical, electrical, and structural properties of the films. All ZnO samples exhibit an average transmittance in visible and near-infrared light range exceeding 80% and a resistivity in the range of (3.2–9.0) × 10−3 Ω·cm when deposited on a borosilicate glass with a refractive index of ≈1.52. The transmittance, band gap, refractive index, and extinction coefficient are rarely affected, while the resistivity only slightly decreases with increasing temperature. This technique provides a wide process window for depositing ZnO thin films. The results revealed that the films deposited at a substrate of 55 °C were highly crystalline with a preferential (1 0 0) orientation. In addition, the grains grow larger as the substrate temperature increases. The electrical properties and reliability of ZnO/PET samples are also studied in this paper.

Studies on magnetron sputtered deposited nanocrystalline tungsten oxide films useful for electrochromic devices

WO3 thin films were sputtered on to different substrates (viz., Si, quartz and ITO coated glasses) at different temperatures and partial pressures using DC magnetron sputtering. The influences partial pressures of O2 and Ar and substrate temperature (at constant sputtering power) on different characteristics viz., optical, structural, morphological, compositional and electrochromism of the films have been investigated. These characteristics were observed to be strongly reliant on deposition conditions. Thickness and roughness (r.m.s.) of the films were found to be in the ranges of 700–918 nm and 3.18–8.4 nm, respectively. The transmittance in the visible wavelength region of these films was found to in the range of 33–80% depending upon the deposition conditions and optical band gap is found to decrease with increase of substrate temperature from 400 K to 600 K at 16.3 mTorr. The X-Ray diffractogram of the films (deposited at 400 K at 16.3 mTorr) exhibited sharp peaks from the reflections of (0 2 1) and (4 2 1) planes of monoclinic crystalline phase of WO3 indicating the prepared films are of crystalline in nature. The structural arrangement of WO3 molecules in the films were analyzed using micro-Raman studies. The morphology studies (using FE-SEM, AFM and EDS techniques) of the films indicated reasonably good stoichiometry of WO3 films; these results further indicated that the films consist of nanoparticles of with sizes varying upon the deposition conditions. For studying the electrochromism of the films, they were immersed in an anhydrous electrolyte (mixture of 0.2 M lithium perchlorate and 50 ml propylene carbonate); coefficient of diffusion of Li+ ions and coloration efficiency were measured by cyclic voltammetry and chrono-coulometry methods, respectively. The partial oxygen pressure and substrate temperature used during deposition were found to influence the above mentioned parameters of the films to a larger extent.

A brief review on the techniques used for the enhancement of luminescence of red emitting thin film

In the past few years, red emitting thin film activated by Eu3+ has received much attention. Europium has a peculiar property that it exhibits both types of emission on the basis of their valencies. In this review, we try to make a full list of known methods which may be useful for the enhancement of luminescence. It has been found that luminescence can be enhanced by increasing substrate temperature, film roughness, changing the morphology etc. Finally we discuss the mechanism of co-doping with different elements for the enhancement of luminescence.

Electrical and Optical Properties of Amorphous SnO2:Ta Films, Prepared by DC and RF Magnetron Sputtering: A Systematic Study of the Influence of the Type of the Reactive Gas

By reactive magnetron sputtering from a ceramic SnO2:Ta target onto unheated substrates, X-ray amorphous SnO:Ta films were prepared in gas mixtures of Ar/O2(N2O, H2O). The process windows, where the films exhibit the lowest resistivity values, were investigated as a function of the partial pressure of the reactive gases O2, N2O and H2O. We found that all three gases lead to the same minimum resistivity, while the width of the process window is broadest for the reactive gas H2O. While the amorphous films were remarkably conductive (ρ ≈ 5 × 10−3 Ωcm), the films crystallized by annealing at 500 °C exhibit higher resistivities due to grain boundary limited conduction. For larger film thicknesses (d ≳ 150 nm), crystallization occurs already during the deposition, caused by the substrate temperature increase due to the energy influx from the condensing film species and from the plasma (ions, electrons), leading to higher resistivities of these films. The best amorphous SnO2:Ta films had a resistivity of lower than 4 × 10−3 Ωcm, with a carrier concentration of 1.1 × 1020 cm−3, and a Hall mobility of 16 cm2/Vs. The sheet resistance was about 400 Ω/□ for 100 nm films and 80 Ω/□ for 500 nm thick films. The average optical transmittance from 500 to 1000 nm is greater than 76% for 100 nm films, where the films, deposited with H2O as reactive gas, exhibit even a slightly higher transmittance of 80%. These X-ray amorpous SnO2:Ta films can be used as low-temperature prepared transparent and conductive protection layers, for instance, to protect semiconducting photoelectrodes for water splitting, and also, where appropriate, in combination with more conductive TCO films (ITO or ZnO).

Morphology and surface properties of Cu thin film on Si (001)

In this work, molecular dynamics simulation was used to expect the effect of incident energy and substrate temperature on the morphology, surface roughness and structure of Cu thin film on Si (001) substrate. Our results indicate that the growth of Cu thin film depend clearly on the incident energy and substrate temperature. It was found that for lower incident energy, the morphology of deposited film is not smooth, and the film mixing is observed and limited to the top layer of substrate, it can be considered as quasi-epitaxial growth mode. Thus, the film-mixing mode is produced when the incident energy increases. In this case, the morphology of deposited film becomes smoother. In addition, the radial distribution function show that with increasing incident energy, the structure of the film deposited changes notably from crystalline structure to an amorphous structure one. As well, the surface roughness and length of film mixing are influenced by the substrate temperature. With the increase of substrate temperature, the surface roughness decreases whereas the length of film mixing increases.

Optoelectronic properties and anisotropic stress of Mo:ZnO thin films deposited on flexible substrates by radio frequency magnetron sputtering.

This research investigated the optoelectronic properties and anisotropic stress of Mo-doped ZnO (MZO) films, which were deposited on polyethylene terephthalate and polycarbonate flexible substrates with radio frequency magnetron sputtering. The optical properties, x-ray diffraction (XRD) spectra, Hall effect measurements, and self-made phase-shift shadow moiré interferometer readings were utilized to evaluate the performances of the MZO films. Based on the results, the transmittance and (002) peak size of the XRD spectra decreased when the substrate temperature increased. However, this took place especially when the oxygen flow was on the increase. Also, carrier mobility, carrier concentration, and anisotropic stresses increased at higher substrate temperatures, but this was not the case when the oxygen flow increased. The energy gap (Eg) of the MZO films showed a blueshift with an increase in the substrate temperatures, but this rather changed to a redshift when the oxygen flow was observed to be on the rise.

Structure and optical properties of HfO2 films on Si (100) substrates prepared by ALD at different temperatures

In this work, HfO2 thin films were deposited on Si (100) wafer by using reactive atomic layer deposition at different temperatures. By characterizing the Raman spectroscopy and XRD patterns, we find that with the substrate temperature increases, the structure of the film transforms continuously, and a substrate with sufficiently high temperature can generate enough energy to produce a film in the crystalline phase. UV–vis absorption spectrum shows that the anti-reflection effect of the deposited HfO2 thin films is effective. The characteristic reflective peak of the film exhibits a slightly blue shift with increasing the substrate temperature, indicating that the thickness of the film decreases as the substrate temperature increases. The refractive index of the visible to near infrared spectral range increases with the increase of temperature, and the film becomes more compact. The surface morphology of HfO2 films was measured by AFM, and the skewness, kurtosis and roughness of the films were also analysed. Increasing substrate temperature has led to improvement in the film uniformity and compactness. The above results indicate that the substrate temperature is a critical parameter in determining the film structure, morphology and optical properties.

Aerosol Jet Printing of Silver Lines with A High Aspect Ratio on A Heated Silicon Substrate.

In this work, we studied the formation of conductive silver lines with high aspect ratios (AR = thickness/width) > 0.1 using the modernized method of aerosol jet printing on a heated silicon substrate. The geometric (AR) and electrical (resistivity) parameters of the formed lines were investigated depending on the number of printing layers (1–10 layers) and the temperature of the substrate (25–300 °C). The AR of the lines increased as the number of printing layers and the temperature of the substrate increased. An increase in the AR of the lines with increasing substrate temperature was associated with a decrease in the ink spreading as a result of an increase in the rate of evaporation of nano-ink. Moreover, with an increase in the substrate temperature of more than 200 °C, a significant increase in the porosity of the formed lines was observed, and as a result, the electrical resistivity of the lines increased significantly. Taking into account the revealed regularities, it was demonstrated that the formation of silver lines with a high AR > 0.1 and a low electrical resistivity of 2–3 μΩ∙cm is advisable to be carried out at a substrate temperature of about 100 °C. The adhesion strength of silver films formed on a heated silicon substrate is 2.8 ± 0.9 N/mm2, which further confirms the suitability of the investigated method of aerosol jet printing for electronic applications.

Substrate Temperature Dependence of TiO2 Films Deposited by Spray Ultrasonic Nebulizer Technique

This work details the growth of nanostructured TiO2 thin films on a glass substrates using the ultrasonic nebulizer technique, deposited at 300-600 °C . The influence of the deposition temperature is linked to the physic-chemical properties of the TiO2 thin films. XRD- results confirmed that the nanostructures tetragonal are polycrystalline, the grain size(s) increases alongside the substrates temperature, and the deposited film is the anatase phase at 400 C. The surface morphology of the deposited film were imaged using the (AFM) technique, and it was confirmed that the films are of excellent crystallinity and are homogeneously dispersed. It was also confirmed that the Root Mean Square (RMS) of the thin films' surface roughness is dictated by the substrate's temperature, which was further confirmed using the SEM technique. The substrate temperature is inversely proportional to the optical energy gap values. The increase in optical gap with increasing substrate temperature can be due to improvement in the films crystallinity .At higher temperatures promote a high mobility of ad-atoms; it allows a better atomic arrangement, which promotes the formation of a crystalline structure.

Optical Investigations of Nanophotonic LiNbO<sub>3</sub> Films Deposited by Pulsed Laser Deposition Method

The nanocrystalline structure of Lithium niobate (LiNbO3) was prepared and deposited onto substrate made of quartz by utilize pulse laser deposition technique. The effect of substrate temperature on the structural, optical and morphological properties of lithium niobate photonic film grown was studied. The chemical mixture was prepared by mixing the raw material (Li2CO3, Nb2O5) with Ethanol liquid without any further purification, at time of stirrer 3hrs but without heating, then annealing process the formed material at 1000C° for 4hrs. We characterized and analyzed the LiNbO3 nanostructure thin films by utilize Ultra-Violet Visible (UV-vis). The UV-vis measurements show that, when the substrate temperature increases, the values of transmission, absorption and energy band gap will decreased, but the values of reflection and refractive index will increased. That means the LiNbO3 thin film prepared at substrate temperatures 300C° give the best result for manufacture the optical waveguide.