Surface Morphology Of Thin Films Research Articles

Effect of Al doping on the Structural properties of SnO2 thin films prepared by (sol-gel) method

Undoped and Al-doped SnO2 thin films have been prepared by sol–gel spin coating process on glass substrate for different doping (0, 2.5 ,5 ,7.5,10)% The starting precursor was used as tin chloride dihydrate (SnCl2.2H2O), ethanol , with and without stabilizer. As annealing in a temperature 500°C for one hours, the results of (X-Ray ) diffraction showed that the films have a Polycrystalline structure and increased intensity when use stabilizer and orientation was (020) with lattice constants (a=4.796, b=5.796, c= 5.193) Å.
 The surface morphology of the (SnO2: Al) thin films have been studied using atomic force microscopy (AFM) which indicated that the grown films showed good crystalline and homogeneous surface. The Root Mean Square (RMS) values and surface roughness of the films increased with increasing doped concentration specify when use stabilizer.

Surface morphology and optical properties of thin films of plasma polymerized methyl acrylate

Thermally stable plasma polymerized methyl acrylate (PPMA) thin films are fabricated onto spotless glass substrates by AC power plasma polymerization technique. Field emission scanning electron micrographs of these films exhibit clusters/agglomerations on the surface. Energy dispersive x-ray analysis confirms the existence of 52.38, 52.63 and 51.55% of carbon and 47.62, 47.31 and 46.45% of oxygen, respectively in 170, 230 and 290 nm thick PPMA films. The molecular vibrations of various natures observed by attenuated total reflectance Fourier transform infrared spectroscopy of methyl acrylate and PPMA represent that the percentage of hydrophilic groups is smaller than the hydrophobic groups. Thermogravimetric analyses demonstrate that the major weight loss occurs in the temperature range from 500 to 850 K. Ultraviolet–visible spectroscopy demonstrates that the allowed direct energy band gap varies from 3.77 to 3.83 eV, whereas the indirect energy band gap alters from 3.40 to 3.48 eV with film thicknesses from 120 to 290 nm. Other optical parameters such as Urbach energy, refractive index, optical extinction coefficient, dielectric constants, quality factor, and skin depth have also been investigated for the PPMA thin films to elucidate their suitability in optoelectronic devices.

Characterization of [1]Benzothieno[3,2-b]benzothiophene (BTBT) Derivatives with End-Capping Groups as Solution-Processable Organic Semiconductors for Organic Field-Effect Transistors

Solution-processable [1]benzothieno[3,2-b]benzothiophene (BTBT) derivatives with various end-capping groups, 2-(phenylethynyl)benzo[b]benzo[4,5]thieno[2,3-d]thiophene (Compound 1), 2-octyl-7-(5-(phenylethynyl)thiophen-2-yl)benzo[b]benzo[4,5]thieno[2,3-d]thiophene (Compound 2), and triisopropyl((5-(7-octylbenzo[b]benzo[4,5]thieno[2,3-d]thiophen-2-yl)thiophen-2-yl)ethynyl)silane (Compound 3), have been synthesized and characterized as active layers for organic field-effect transistors (OFETs). Thermal, optical, and electrochemical properties of the newly synthesized compounds were characterized using thermogravimetric analysis (TGA), a differential scanning calorimeter (DSC), UV–vis spectroscopy, and cyclic voltammetry (CV). Thin films of each compound were formed using the solution-shearing method and the thin film surface morphology and texture of the corresponding films were characterized using atomic force microscopy (AFM) and θ–2θ X-ray diffraction (XRD). All semiconductors exhibited p-channel characteristics in ambient and Compound 1 showed the highest electrical performance with a carrier mobility of ~0.03 cm2/Vs and current on/off ratio of ~106.

Effect of different sulfur pressure annealing on properties of sputtering-deposited ZnS thin films

ZnS, a kind of wide-band gap semiconductor, has attracted extensive attention in recent years due to its excellent photoelectric performance, which has broad application prospects in solar cells, photocatalysts and sensors. In this work, ZnS thin films are first deposited by radio-frequency (RF) magnetron sputtering, and then annealed at 600 ℃ and different sulfur pressures. The crystal structure, surface morphology, grain size, composition, transmittance and defects of ZnS thin films are analyzed by X-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy, UV-vis transmission spectra, and positron annihilation Doppler broadening spectroscopy. The results show that the crystallinities of ZnS films can be improved by being annealed in sulfur atmosphere, and the optical band gaps of ZnS films after being annealed are in a range of 3.43–3.58 eV. When the sulfur pressure is higher than 0.49 atm, the sulfur interstitial atoms in the ZnS and the elemental sulfur on the surface reduce the transmittance of the film in the visible region. The Doppler broadening spectroscopy results also show that the defect concentrations of ZnS films decrease gradually from their surface layers to the inner layers, and the defects of ZnS films decrease with the increase of sulfur pressure. Meanwhile, the 3γ annihilation also proves that the interior of the film is relatively dense, and the open porosity of the film will increase due to vulcanization. Adsorbed sulfur occupies the position of sulfur vacancy defect in the crystal through internal diffusion, which leads the defect concentration to decrease and the film quality to be improved.

Effect of oxygen defects on microstructure, optical and vibrational properties of ScN films deposited on MgO substrate from experiment and first principles

We report on the effects of oxygen impurities on the microstructure, surface morphology, optical absorption, and vibrational properties of scandium nitride thin films deposited onto magnesium oxide substrate by reactive magnetron sputtering and under ultrahigh vacuum conditions. Two distinct deposition temperatures of 700°C and 800°C were applied to adjust the level of oxygen contamination. The ScN/MgO(001) thin films have been characterized by various spectroscopic methods, including X-ray diffraction, X-ray photoelectron spectroscopy, atomic force microscopy, Raman spectroscopy, and optical microscopy. The ScN films deposited at the lower temperature of the MgO substrate show higher content of defects, stronger disorientation, a larger concentration of twin domains, and suppressed adatom mobility as compared to layers deposited at the higher temperature. An increase by 2% in the amount of accommodated oxygen results in the increase in the direct energy gap of the ScN films by about 0.13 eV, which follows from the increased concentration of the n-type charge carriers incorporated by oxygen impurities. The observed increase in the absorption edge, i.e., enlargement of the optical band gap can be accounted for the Burstein–Moss effect. Experimental Raman spectra reveal coupling between longitudinal optic phonons and electronic states, which can be described by the Fano-type function with the asymmetry parameter increasing with increased content of oxygen defects. The ab initio Raman spectra of ScN with concentrations of oxygen impurities corresponding to the respective experimental values, obtained within density functional theory, demonstrate that incorporated impurities affect significantly the phonon dynamics via modified force constants, including those at atoms beyond the nearest neighbors of defects. The simulated Raman spectra reflect major features of the experimentally determined spectral patterns enabling better insight into the origin of changes experienced by the oxygen-modified ScN/MgO(001) films.

Piezoelectric and Magnetoelectric Effects of Flexible Magnetoelectric Heterostructure PVDF-TrFE/FeCoSiB.

Flexible polymer-based magnetoelectric (ME) materials have broad application prospects and are considered as a new research field. In this article, FeCoSiB thin films were deposited on poly(vinylidene fluoride-co-trifluoroethylene) (PVDF-TrFE) substrate by DC magnetron sputtering. The structure of PVDF-TrFE/FeCoSiB heterostructure thin films was similar to 2-2. Under a bias magnetic field of 70 Oe, the composites have a dramatically increased ME voltage coefficient as high as 111 V/cm⋅Oe at a frequency of about 85 kHz. The piezoelectric coefficient of PVDF-TrFE thin films is 34.87 pC/N. The surface morphology of PVDF-TrFE thin films were studied by FESEM, and the results of XRD and FTIR showed that the β-phase of PVDF-TrFE thin films was dominant. Meanwhile, the effects of different heating conditions on the crystallization and piezoelectric properties of PVDF-TrFE films were also studied. The flexible ME heterojunction composite has a significant ME voltage coefficient and excellent piezoelectric properties at room temperature, which allows it to be a candidate material for developing flexible magnetoelectric devices.

Orientation control of Platinum electrode grown on silicon using [Ca2Nb3O10]− nanosheets as seed layer.

Platinum (Pt) is a noble metal with low resistivity and resilience to oxidation, which is largely used in microelectronic devices. In order to facilitate the integration of Pt thin films on silicon substrate, we are showing the ability to control their orientation by using [Ca2Nb3O10]− nanosheets (CNOns) as seed layer. Pt thin films were sputtered on silicon coated by CNOns (CNOns/SiO2/Si), and on TiO2/SiO2/Si substrates for comparison, at temperatures ranging from room temperature up to 625°C. Under pure argon, highly (111) textured Pt thin films were obtained on both substrates, regardless of the deposition temperature. However, by using an oxygen/argon mixture, highly (200) textured films could be obtained, only on CNOns/SiO2/Si substrate, when the substrate temperature is above 550°C. X-ray diffraction, scanning electron microscopy, and atomic force microscopy were used to characterize the crystalline quality, thickness, surface morphology and roughness of the Pt thin films. Their resistivity was measured at room temperature by the four-point probes method.

Synthesis of Vacancy-Controlled Copper Iodide Semiconductor for High-Performance p-Type Thin-Film Transistors.

Copper iodide (CuI) has emerged as a promising p-type semiconductor material owing to its excellent carrier mobility, high transparency, and solution processability. Although CuI has potential for numerous applications, including perovskite solar cells, photovoltaic devices, and thin-film transistors (TFTs), the close relationship between the anion vacancy generation and the charge transport mechanism in CuI-based devices is underexplored. In this study, we propose solution-processed p-type CuI TFTs which were subject to the thermal annealing process in air and vacuum atmospheres at temperatures of 100, 200, and 300 °C. The chemical states and surface morphologies of the CuI thin films were systematically investigated, revealing the generation of iodine vacancy states and the reduction of carrier concentration, as well as increased film density and grain size according to the annealing condition. Further, the effective role of the Al2O3 passivation layer on the electrical characteristics of the solution-processed CuI TFTs is demonstrated for the first time, where the Al2O3 precursor greatly enhanced the electrical performance of the CuI TFTs, exhibiting a field-effect mobility of 4.02 cm2/V·s, a subthreshold swing of 0.61 V/decade, and an on/off current ratio of 1.12 × 104, which exceed the values of CuI TFTs reported so far. Based on the synergistic effects of the annealing process and the passivation layer that engineered the iodine vacancy state and morphology of CuI, the proposed CuI TFTs with the Al2O3 passivation layer showed excellent reliability under 100 times repeated operation and long-term stability over 216 h, where the transfer curves slightly shifted in the positive direction of 1.36 and 1.88 V measured at a current level of 10-6 A for the reliability and stability tests, respectively. Thus, this work opens a new window for solution-processed p-type CuI TFTs with excellent stability for developing next-generation complementary logic circuits.

TiO2–Graphene Oxide and TiO2–Reduced Graphene Oxide Composite Thin Films for Solar Photocatalytic Wastewater Treatment

This research reports on Vis- and solar-active photocatalytic bi-layered films of TiO2 (layer 1) and a composite with TiO2 matrix and graphene oxide or reduced graphene oxide filler (layer 2) obtained by coupling two methods: spray pyrolysis deposition followed by spraying a diluted sol. The thin films crystallinity degree, surface morphology and elemental composition were recorded and the composites were tested in photo-degradation processes, using the standard 10 ppm methylene blue solution, under simulated UV + VIS irradiation conditions using an irradiance measured to be close to the natural one, in continuous flow process, at demonstrator scale; these results were compared with those recorded when using low irradiance values in static regime. The effect of the increase in the graphene oxide content was investigated in the concentration range 1.4%w...10%w and was found to increase the process efficiency. However, the photocatalytic efficiencies increased only by 15% at high irradiance values compared with the values recorded at low irradiance as result of the electron-hole recombination in the composite-thin film. Similar experiments were run using composites having reduced graphene oxide as filler. The interfaces developed between the matrix and the filler were discussed outlining the influence of the filler’s polarity. The thin films stability in aqueous medium was good, confirmed by the results that outlined no significant differences in the surface aspect after three successive photocatalytic cycles.

Solar-blind photodetectors fabricated on β-Ga2O3 films deposited on 6° off-angled sapphire substrates

In this paper, the β-Ga2O3 films were deposited on 6° off-angled (towards <11–20> direction) (0001) sapphire substrates by MOCVD, and the MSM structure solar-blind photodetectors were fabricated. The effects of growth temperature on the surface morphology, elemental composition, crystalline quality and optical properties of β-Ga2O3 thin films were investigated. As the substrate temperature increased from 650 to 850 °C, the surface RMS roughness of the film gradually increased, and the bandgap was 4.71, 4.73 and 4.76 eV, respectively. In addition, the photodetector fabricated on β-Ga2O3 film at 850 °C exhibited a large photocurrent (Iphoto) of 0.59 mA, a high responsivity (R) of 1.26 A/W, a high photo-to-dark current ratio (PDCR) of 9.3 × 104, a detectivity (D*) of 2.5 × 1012 Jones, and a fast response recovery time of 0.38 s.

Effect of Deposition Temperature on the Surface, Structural, and Mechanical Properties of HfO2 Using Chemical Vapor Deposition (CVD)

A high-temperature-resistant and high-performance hafnium oxide (HfO2) coating for aerospace engines was developed. HfO2 thin film coatings were prepared by chemical vapor deposition (CVD) at 1200, 1250, 1300, and 1350 °C, respectively. The crystal structure and surface morphology of the HfO2 thin films at different deposition temperatures were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), and atomic force microscopy (AFM). The effect of deposition temperature on the mechanical properties of the HfO2 thin films was studied by means of the drainage method and nanoindentation. The results showed that the HfO2 coatings deposited at different deposition temperatures are monoclinic crystal structures, and the surface morphology changes from cellular particles to columnar particles, and finally, to a loose and porous layered structure. When the deposition temperature is 1300 °C, the density of the HfO2 film is the highest, 9.62 ± 0.03 g/cm3, and the hardness is the highest, 7.33 ± 0.04 GPa. A HfO2 coating with the best comprehensive mechanical properties was prepared by changing the deposition temperature, which provided an experimental basis for the application of a HfO2 coating in the aerospace field.

Electrical charge transport and surface morphology of In2S3 thin films doped with Cu

In the present work, the transport properties and morphology through tunneling structures were investigated, where the rough In2S3 thin films are the interfaces of these structures. In2S3 thin films were doped experimentally with Copper (Cu) and their morphology was studied by using the atomic force microscopic images at different temperatures (30, 55, 70, and 85). The results show that conductivity of the samples is strongly influenced by Cu doping content at different temperatures. Also, the transmission probability and current density of these samples were investigated numerically. The results show the maximum scattering component of transmission probability at temperature 30 for In2S3 thin films and 70 for CuIn2S3 thin films. By the results, increasing of the [Cu/In] molar ratios will lead to an increase in the transmission probability and current density of these thin films.

Structural, Electrical and Optical Properties of Mg-Ni Thin Films for Hydrogen Storage Applications

Using the magnetron sputtering technique, Mg-Ni (150nm) bilayer thin films were deposited onto the simple, and ITO coated glass substrates. To obtain proper mixing and inter diffusion of thin film structure, annealing of the prepared thin films was made at constant temperature 523 K. The surface morphology of thin films confirms the uniform deposition of the Mg-Ni thin films on substrates. The Raman spectroscopy of thin films shows that the intensity of Raman peaks is decreased as the hydrogen pressure increases and variation in the intensity peak confirms the existence of hydrogen in the prepared film. The d.c. conductivity of thin films were observed at different hydrogen pressure (10 - 40 psi) for both the as-deposited and annealed thin films and the variation in the conductivity after hydrogenation was found out. In Uv-Vis spectroscopy, it was found that the optical bandgap of thin films increases with the increase of hydrogen pressure. The deviations in the structural, electrical and optical properties after hydrogenation indicate that Mg-Ni thin films may be used for solid state hydrogen storage applications. HIGHLIGHTS Preparation of Mg-Ni bilayer thin films using magnetron sputtering technique Finding the opportunity to use Mg-Ni bilayer thin film as solid-state hydrogen storage materials Raman spectroscopy for confirming the presence of hydrogen in Mg-Ni bilayer thin films Effect of hydrogen on conductivity and optical energy bandgap of Mg-Ni bilayer thin films GRAPHICAL ABSTRACT

Effect of vanadium precursor on dip-coated vanadium oxide thin films

The effect of chemical substances is reported on the structure, surface morphology, and material properties of vanadium oxide thin films. The study of the chemical substances concentrated on the effects of initial materials (e.g., NH4VO3, NaVO3, VO2, vanadyl acetylacetonate, ammonium decavanadate) and various additives (e.g., acids, chelate ligand, reduction reagent, and tensides). The syntheses are based on sol-gel chemistry. The important aim of the sol-gel technique was to optimize the chemical conditions such as catalyst and solvent for the preparation of perfect V5+-containing layers. The other aim was to check the controllability of the V4+/V5+ ratios. The control was performed in the air by using a reducing agent and in a nitrogen atmosphere. The atomic and bond structures were investigated by 51V MAS NMR, IR, and UV spectroscopies. The supramolecular structures were determined by SEM, EDX, and GIXRD techniques.Graphical abstract

Effects of the SiO2 underlayer on magnetic properties of the Pr-Fe-B thin film

Si3N4/Pr-Fe-B/SiO2 thin films were deposited by magnetron sputtering on Si (100) substrate with in-situ annealing at 650 °C. The magnetic properties of these thin films showed significant changes at the various thicknesses of the SiO2 underlayer. This resulted from various growth and orientations of the Pr2Fe14B hard-magnetic phase, and a new Fe3Si underlayer was differently formed at the interface of the Pr-Fe-B layer/SiO2 underlayer. It also led to changes in surface morphology and microstructure of thin films. Coercivity showed a considerable increment at the 75 nm thickness. A better perpendicular anisotropy was found at 20 and 50 nm thicknesses, although coercivities were lower at these thicknesses. Oxygen composition showed an insignificant effect on the magnetic properties of Pr-Fe-B thin film.

Ionic liquid modulation of exchange bias in epitaxial LaMnO3 thin films

The magnetic ground state of LaMnO3 (LMO) thin film is still a controversial issue, even though various mechanisms, such as cation/anion non-stoichiometry, epitaxial strain, interfacial charge reconstruction, and orbital ordering, have been proposed. Here, exchange bias (EB) was introduced into a high-quality epitaxial LMO thin film via relatively low oxygen growth pressure. The EB in LMO was modulated by +2 V gating via ionic liquid method with increased EB field (HEB), coercivity (HC), blocking temperature (TB), and reduced ferromagnetic (FM) magnetization. However, the −2 V gating has a much weaker tunability. By investigating the change of structure, surface morphology, and Mn oxidation state in LMO thin films, the modulation of magnetic properties is attributed to the creation/annihilation of oxygen vacancy in an LMO thin film. The suppressed FM phase in LMO can be ascribed to reduced Mn valence, structure disorders, and structure transition. However, the enriched antiferromagnetic phase results from the transition of the pseudocubic structure to the distorted orthorhombic structure. This work not only highlights the importance of functional defects in perovskite oxides but also sheds light on the potential of electric-field modulation of magnetism in spintronic devices.

Controlled Surface Morphology and Electrical Properties of Sputtered Titanium Nitride Thin Film for Metal–Insulator–Metal Structures

Titanium nitride (TiN) is a material of interest for electrodes owing to its high-temperature stability, robustness, low-cost, and suitable electrical properties. Herein, we studied the surface morphology and electrical properties of TiN thin film deposited onto an Si/SiO2 &lt;100&gt; substrate through direct current (DC) sputtering with a high-purity TiN target in an argon-gas environment. The electrical properties and surface morphology of TiN thin film significantly improved with increased source power and decreased working pressure. The improved electrical properties could be attributed to the suppressed secondary phase (Ti2N) formation and the reduced electron scattering on smoother surface. Consequently, high-quality TiN thin film with the lowest resistivity (ρ = 0.1 mΩ·cm) and the smallest surface roughness (RMS roughness, Rq = 0.3 nm) was obtained under the optimized condition. The TiN film was further used as the bottom electrode for a metal–insulator–metal (MIM) capacitor. Results demonstrated that the electrical properties of TiN film were comparable to those of noble-metal thin films. Therefore, the TiN thin film fabricated by DC sputtering method had excellent electrical properties and good Rq, indicating its potential applications in MIM capacitors and Si technology.

Study on Preparing β-Ga2O3 Films with Temperature-Controlled Buffer Layer by RF Magnetron Sputtering

β-Ga2O3 thin films were prepared on (0006) sapphire substrates by RF magnetron sputtering. Under the conditions of sputtering power of 80 W, time of 10 min, and total flow rate of 40 sccm in oxygen and argon atmosphere (2.5 % oxygen ratio). Different preparation temperatures were used to conduct layering by temperature modulation. A homogenous β-Ga2O3 buffer layer was grown first, and then the second β-Ga2O3 film was grown on top of it. When the stratified sputtering of different temperature combinations was completed, high-temperature thermal annealing with the same parameters was performed. The effects on the structure, surface morphology, and optical properties of β-Ga2O3 thin films were compared and analyzed when using the preparation sequence of the homogenous buffer layer and the top layer at different temperatures after annealing. Finally, based on the stratified preparation temperature parameters, the optimal stratified temperature parameters were summarized.

Surface microstructures and oxygen evolution properties of cobalt oxide deposited on Ir(111) and Pt(111) single crystal substrates

AbstractWe investigated the oxygen evolution reaction (OER) activity changes of cobalt oxide (CoOx) thin films on Ir(111) and Pt(111) substrates by repeated OER measurements in 0.1 M KOH. Atomic force microscopy and X‐ray photoelectron spectroscopy analysis of the as‐prepared CoOx/Ir(111) and CoOx/Pt(111) showed similar surface morphologies of the CoOx thin films and almost the same OER overpotentials, which were estimated to be around 430 mV. However, after three OER measurements, the overpotential of CoOx/Ir(111) decreased by 70 mV, whereas that of CoOx/Pt(111) increased slightly. Structural analysis showed that CoOx/Ir(111) revealed the island‐like nanostructures of CoOx dispersed on Ir(111) surface, accompanied by the generation of CoOOH. In contrast, for CoOx/Pt(111), the Pt(111) substrate remains covered by the CoOx thin film. The results suggest that the interaface at CoOx (CoOOH) nano‐islands and Ir(111) substrate are responsible for reducing the OER overpotential.

Modification of alkyl side chain on thiophene-containing benzothieno[3,2-b]benzothiophene-based organic semiconductors for organic field-effect transistors

In this study, three new organic semiconductors based on benzothieno[3,2-b]benzothiophene with double thiophene rings and different types of alkyl side chains were synthesized and characterized as active layers for organic field-effect transistors. Physicochemical properties of the newly synthesized organic compounds including thermal, optical, and electrochemical properties were characterized through thermogravimetric analysis (TGA), differential scanning calorimeter (DSC), UV–vis spectroscopy, and cyclic voltammetry (CV). The thin film surface morphology and texture of all three compounds fabricated by solution-shearing process were analyzed via atomic force microscopy (AFM) and θ-2θ X-ray diffraction (XRD). All semiconductor thin films showed p-channel activity and the compound with monoalkylated 2-ethylhexyl group as a substituent exhibited the highest electrical performance with carrier mobility of 0.033 cm2/Vs and current on/off ratio of ∼106.