Surface Morphology Of Thin Films Research Articles

Single crystal structure of cobalt and nickel complexes constructed by imidazole ligand and their polycrystalline thin films for nonlinear optical refraction properties

The single crystals of new cobalt and nickel complexes constructed by the imidazole ligand: hexakis(imidazole)-cobalt(II) dichloride tetrahydrate ((C18H24N12Co)Cl2•4(H2O), HICDCTH) and hexakis(imidazole)-nickel(II) acetate dihydrate ((C18H24N12Ni)(CH3COO)2•2(H2O), HINADH) have been obtained and their single crystal structure were determined by X-ray single crystal diffraction. Their polycrystalline thin films on quartz substrates were prepared using in-situ crystallization methods. The surface morphology of the polycrystalline thin films were studied by atomic force microscopy. The nonlinear optical refraction properties of the polycrystalline thin films were investigated by using closed aperture Z-scan technique with 20 picosecond pulses at wavelength 532 nm. Time-dependent density-functional theory with the basis set LanL2DZ were used in theoretically computing their maximum absorption wavelengths, frontier molecular orbitals and molecule′s second hyperpolarizability γ values.

The influence of the physicochemical nature of the components of the V2O5/GaAs, MnO2/GaAs, V2O5/InP, MnO2/InP, TiO2/InP, and SnO2/InP heterostructures and the oxidation conditions on the surface morphology of the synthesised films

The formation of oxide functional films on the surface of semiconductors is a serious technological challenge, which is even more complicated in the nanometre thickness range. It is necessary to form films with specified values of thickness, resistivity, and a certain surface morphology for practical applications. Such films are used in micro- and optoelectronics, environmental monitoring, and alternative energy devices. The goal of this work is to establish the features of the surface morphology of thin films formed as a result of the thermal oxidation of the MnO2/GaAs, V2O5/GaAs, V2O5/InP, MnO2/InP, TiO2/InP, and SnO2/InP heterostructures depending on the physicochemical nature of the components and the oxidation conditions. The synthesis of thin films on the InP and GaAs surfaces was carried out by thermal oxidation under the influence of magnetron-deposited layers of chemostimulator-modifiers. The thickness of the formed films and their composition were determined by laser ellipsometry, X-ray phase analysis, and infra-red spectroscopy. The scanning tunnel and atomic force microscopy were used to determine the morphological characteristics of the films and their dependence on the type of semiconductor substrate, the nature of the chemostimulator-modifier, and the conditions of the thermal oxidation. The application to the GaАs and InP surfaces of the most effective chemostimulator-modifiers (V2O5 and MnO2) of thermal oxidation and higher temperatures of the oxidation process contributed to the formation of smoother and nanostructured films.

Effect of Ga doping on microstructure, morphology, optical and electrical properties of spray deposited CdO thin films

Cadmium oxide (CdO) and gallium (Ga) doped CdO thin films were fabricated successfully onto glass substrate at 400 °C temperature by spray pyrolysis technique and the effect of Ga on microstructure, surface morphology, optical, electrical and Hall effect properties of CdO thin films have been revealed and discussed. X-ray diffraction results indicate that all films are polycrystalline and possess cubic crystal structure. The SEM images reveal that the surface morphology of CdO changes remarkably with increasing Ga doping concentration. EDX investigation confirms the presence of cadmium (Cd), oxygen (O) and gallium (Ga) elements in the deposited films. The optical transmittance of CdO increases continuously with Ga doping up to 3% and then decreases onwards within the same wavelength region. The optical band gap initially increases from 2.47 eV to 2.53 eV, and Urbach energy decreases from 0.55 eV to 0.50 eV when the doping of Ga varies from 0 to 3%. Thereafter, the extinction coefficient, refractive index and energy dissipation factor shows reverse relation above 3% doping of Ga. The electrical resistivity of CdO thin film has been found 5.79 × 10−4 (ohm-cm) and which reduces to 1.23 × 10−4 (ohm-cm) for 3% Ga doping. The temperature dependent electrical resistivity data of deposited films shows that the films possess poor metal-like behaviour. Results of Hall Effect measurement notifies that the carrier of the films is n-type, and Ga doping changes the Hall mobility & carrier concentration of CdO films significantly. The obtained figure of merit of all films is higher than 1.0% Ω−1 and the maximum FOM was found for 3% (8.28 %Ω−1) Ga doped CdO films.

Study of the surface chemistry, surface morphology, optical, and structural properties of InGaN thin films deposited by RF magnetron sputtering

InGaN thin films were deposited on silicon (100) single crystal substrates by RF magnetron sputtering in an Ar atmosphere, at a pressure of 8 × 10−2 Torr, by using In and GaN targets. To change the In content, x, in the InxGa1-xN ternary alloy, the substrate temperature was varied from 300 up to 500 °C. It was found that the In content decreased with increasing substrate temperature. The optical and structural properties of the InGaN thin films were correlated with the experimental deposition conditions. It was found that the band gap energy increased with the growth temperature. Photoluminescence spectra measured at 20 K showed two broad emission bands centered at 2.3 and 2.9 eV. X-ray diffraction analysis of the InGaN thin films revealed a polycrystalline structure belonging to the hexagonal phase. The surface morphology of the films was analyzed using AFM, showing that the surface roughness increased with temperature. The surface chemistry of the films, investigated by XPS, mainly indicated the formation of Ga-N and In-N bonds. Moreover, from XPS two BVM values at 1.91 and 2.74 eV were found. A depth profile analysis, performed by SIMS, revealed the distribution of In, Ga, and N from the film surface to the bulk.

Ruddlesden\u2013Popper 2D perovskites of type (C6H9C2H4NH3)2(CH3NH3)n\u22121PbnI3n+1 (n\u2009=\u20091\u20134) for optoelectronic applications

Ruddlesden–Popper (RP) phase metal halide organo perovskites are being extensively studied due to their quasi-two dimensional (2D) nature which makes them an excellent material for several optoelectronic device applications such as solar cells, photo-detectors, light emitting diodes (LEDs), lasers etc. While most of reports show use of linear carbon chain based organic moiety, such as n-Butylamine, as organic spacer in RP perovskite crystal structure, here we report a new series of quasi 2D perovskites with a ring type cyclic carbon group as organic spacer forming RP perovskite of type (CH)2(MA)n−1PbnI3n+1; CH = 2-(1-Cyclohexenyl)ethylamine; MA = Methylamine). This work highlights the synthesis, structural, thermal, optical and optoelectronic characterizations for the new RP perovskite series n = 1–4. The demonstrated RP perovskite of type for n = 1–4 have shown formation of highly crystalline thin films with alternate stacking of organic and inorganic layers, where the order of PbI6 octahedron layering are controlled by n-value, and shown uniform direct bandgap tunable from 2.51 eV (n = 1) to 1.92 eV (n = 4). The PL lifetime measurements supported the fact that lifetime of charge carriers increase with n-value of RP perovskites [154 ps (n = 1) to 336 ps (n = 4)]. Thermogravimetric analysis (TGA) showed highly stable nature of reported RP perovskites with linear increase in phase transition temperatures from 257 °C (n = 1) to 270 °C (n = 4). Scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDAX) are used to investigate the surface morphology and elemental compositions of thin films. In addition, the photodetectors fabricated for the series using (CH)2(MA)n−1PbnI3n+1 RP perovskite as active absorbing layer and without any charge transport layers, shown sharp photocurrent response from 17 nA/cm2 for n = 1 to 70 nA/cm2 for n = 4, under zero bias and low power illumination conditions (470 nm LED, 1.5 mW/cm2). Furthermore, for lowest bandgap RP perovskite n = 4, (CH)2MA3Pb4I13 the photodetector showed maximum photocurrent density of ~ 508 nA/cm2 at 3 V under similar illumination condition, thus giving fairly large responsivity (46.65 mA/W). Our investigations show that 2-(1-Cyclohexenyl)ethylamine based RP perovskites can be potential solution processed semiconducting materials for optoelectronic applications such as photo-detectors, solar cells, LEDs, photobatteries etc.

Side chain engineering of [1]benzothieno[3,2-b]benzothiophene (BTBT)-based semiconductors for organic field-effect transistors

[1]benzothieno[3,2-b]benzo-thiophene (BTBT)-based compounds with different side chains, 2-(2-ethylhexyl)benzo[b]benzo[4,5]thieno[2,3-d]thiophene (compound 1), 2-(2-ethylhexyl)−7-(thiophen-2-yl)benzo[b]benzo[4,5]thieno[2,3-d]thiophene (compound 2), 2-(2-ethylhexyl)−7-(5-octylthiophen-2-yl)benzo[b]benzo[4,5]thieno[2,3-d]thiophene (compound 3), and 2-(2-ethylhexyl)−7-(5-(2-ethylhexyl)thiophen-2-yl)benzo[b]benzo[4,5]thieno[2,3-d]thiophene (compound 4), were synthesized and characterized as solution-processable small molecular organic semiconductors for organic field-effect transistors (OFETs). The corresponding compounds were employed as active layers for top-contact/bottom-gate OFETs via solution-shearing method and the electrical properties were investigated. The resulting devices exhibited p-channel activity and, especially, thin films of monoalkylated BTBT with additional thiophene ring showed the highest hole mobility up to 0.12 cm2/Vs and current on/off ratio over 107. The analysis of atomic force microscopy (AFM) and X-ray diffraction (XRD) were carried out to correlate surface morphology and microstructure of thin films with the device performance.

Enhancing the ultraviolet photosensing properties of nickel oxide thin films by Zn–La co-doping

In this work, co-doping effects of transition (Zn) and rare-earth (La) elements on the crystalline structure, surface morphology, photoluminescence, optical and photosensing properties of NiO thin films are studied. NiO, NiO:Zn(1%), NiO:La(1%), and NiO:Zn(1%):La(1%) thin films are fabricated using the nebulizer spray pyrolysis (NSP) method. X-ray diffraction study revealed the cubic NiO structure of all the films. Photoluminescence (PL) spectra of thin films exhibit various emission peaks centered at the wavelengths of 387, 414, 437, 451, 477, and 521 nm. The optical bandgap energy ( E g ) values are found to be 3.46, 3.43, 3.39 and 3.33 eV for NiO, NiO:Zn(1%), NiO:La(1%) and NiO:Zn(1%):La(1%) thin films, respectively. The fabricated (Zn, La) co-doped NiO i.e., NiO:Zn(1%):La(1%) photo-detector exhibits highest responsivity ( R ), external quantum efficiency (EQE) and detectivity ( D *) values of 0.50AW -1 , 169% and 14.5 × 10 9 Jones, respectively as compared to NiO, NiO:Zn(1%) and NiO:La(1%) photo-detectors. The present study revealed that the transition and rare-earth elements co-doping can be an effective approach for tuning the various physical properties of semiconducting oxide films.

Characterization of optimized properties for InGaZnO semiconductor and thin film transistor by oxygen partial pressure

The InGaZnO thin films with varied the O2 flow ratios were deposited by a magnetron sputtering system. The effect of O2 content on the structure, surface morphology, optical and electrical properties of InGaZnO thin films is studied. Then, we investigate the relationship between bias stress stability and density of states (DOS) of thin film transistors (TFTs) with various oxygen partial pressure InGaZnO (IGZO) as the channel layer. The temperature-dependent field-effect measurements are used to calculate DOS of IGZO TFTs. With the increase of the oxygen partial pressure, the value of DOS decreases from 2.2 × 1016 to 5.5 × 1015 cm-3. Moreover, the positive gate bias stress of IGZO TFTs are investigated. Under positive gate bias stress, the transfer curves of IGZO TFTs with various oxygen partial pressure show an obvious shift, the value of threshold voltage shift () is 5.1, 2.94, 2 and 0.8 V, respectively. The results suggest that the device with a smaller DOS is more stable than others. Therefore, this study offers a brief and accurate method to demonstrate instability mechanism of IGZO TFTs.

Structural and optical characteristics of thermally evaporated TlGaSe2 thin films

The present paper reports the structural and optical properties of thermally evaporated TlGaSe2 thin films. X-ray diffraction pattern of evaporated film presented two diffraction peaks around 24.15 and 36.00° which are associated with planes of monoclinic unit cell. Surface morphology of the TlGaSe2 thin films was investigated by scanning electron and atomic force microscopy techniques. Although there was observed some ignorable amount of clusters of quasi-spherical shape in the scanning electron microscope image, the film surface was observed almost uniform. Raman spectrum exhibited six peaks around 253, 356, 488, 800, 1053 and 1440 cm−1 associated with possible vibrational mode combinations. Band gap energy of the thin film was determined as 3.01 eV from the analyses of transmission spectrum. Transmission spectrum presented strong Urbach tail and analyses of corresponding region resulted in Urbach energy of 0.66 eV. The structural and optical properties of deposited TlGaSe2 thin films were compared with those of single crystal. This comparison would provide valuable information about influence of thickness on the studied compounds.

Synthesis, characterization and supercapacitive application of nanocauliflower-like cobalt tungstate thin films by successive ionic layer adsorption and reaction (SILAR) method

For the first time, cobalt tungstate (CoWO4) thin films were synthesized by successive ionic layer adsorption and reaction (SILAR) method. The monoclinic crystal structure of CoWO4 film was confirmed from X-ray diffraction (XRD) technique. The elemental, surface morphological, structural, and electrical analyses were executed using Fourier transform infrared spectroscopy (FT-IR), field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray analysis (EDAX), X-ray photoelectron spectroscopy (XPS), Brunauer-Emmett-Teller (BET), two point probe method, and contact angle measurement techniques. The surface morphology of CoWO4 thin film consisted of islands of agglomerated cauliflower-like spherical nanoparticles with hydrophilic nature. The specific surface area of 60 m2 g−1 with an average pore size of 1.10 nm. The CoWO4 thin film electrode exhibited specific capacitance of 1436.5 F g−1 at a scan rate of 2 mV s−1 in 1 M KOH as well as capacitance retention of 94% over 3000 galvanostatic charge discharge (GCD) cycles. Furthermore, flexible solid-state symmetric supercapacitor (FSS-SSC) device assembled using CoWO4 thin films, showed specific capacitance of 101.32 F g−1, specific energy of 14.07 Wh kg−1 and specific power of 1225.25 W kg−1. This work highlights simplistic preparation of CoWO4 thin films for energy storage application.

Transparent SiOxCyHz Barrier Film Prepared by Roll to Roll PECVD

This paper uses plasma-enhanced chemical vapor deposition (PECVD) to successfully fabricate silicon oxide films on silicon dioxide substrates for supporting layers of uncooled infrared focal plane array microbridge structures. In this paper, the thickness, refractive index, growth rate, and other parameters of the films were measured using the XP-2 step meter and ellipsometer. At the same time, atomic force microscopy (AFM) was used to study the surface morphology of the films. The experimental results show that deposition temperature and ICP power are the main factors affecting the growth rate of thin films. Deposition temperature is a crucial factor affecting the surface morphology of thin films.

Качественный и количественный анализ морфологии поверхности порфириновых пленок

The surface morphology of tetraphenylporphyrin thin polycrystalline films – H2TPP and ZnTPP obtained by vacuum condensation under quasi-equilibrium conditions is analyzed by sc. The use of analytical methods for processing images of the organic films surface obtained by standard methods, allows to identify not only qualitative, but also quantitative characteristics of the polycrystalline films structure: the average grain size, grain size distribution, the presence of texture and characteristic of crystallites orientations. It is shown that free based H2TPP tetraphenylporphyrin films have a more pronounced texture and a larger crystallite size than ZnTPP, which is due to the peculiarities of self-organization of molecules, if condensation occurs under the same conditions. The applicability of this method of image analysis for obtaining information about the structure and morphology of the surface of thin organic films during vacuum condensation is shown.

Influence of Synthesizing Temperatures on the Crystallinity, Morphology and Band Gap of CdSe Thin Films

CdSe thin films were deposited using Chemical Bath Deposition (CBD) by maintaining the bath at 20 °C, 40 °C, 60 °C and 80 °C temperatures. The thin films were deposited on ordinary glass substrates then characterized for their crystallinity, morphological and optical properties. From the X-ray Diffraction (XRD) analysis; it was revealed that there was a significant difference in crystallinity and the UV-vis spectroscopy enhanced the study of the energy band gaps which showed a drastic shifting. The study performed on the surface morphologies of the CdSe thin films exhibited a double layer of deposition; but did not show considerable difference from each other for different temperatures. The EDS pattern helped in determining the stoichiometric ratio.

Termal Buharlaştırma ile Üretilen Cu2-xSe İnce Filmlerin Yapısal, Morfolojik ve Optik Özellikleri Üzerine Araştırma

In this work, the influence of post-annealing on the structural, morphological, and optical properties of copper selenide thin films deposited on glass substrate by thermal evaporation was investigated in detail. The post-annealing process at different ambient temperatures in a nitrogen atmosphere was applied to thin films deposited at room temperature. The X-ray diffraction (XRD) patterns showed the presence of cubic Cu2-xSe phase, and it was observed that the crystallinity improves with increasing annealing temperature. In addition, it was deduced that the average crystallite size increased with the annealing temperature. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) were employed to investigate the surface morphology of thin films. It was seen that all samples have compact and densely packed surface morphology and grains on the surface become larger. Surface roughness increased from 11nm to 53 nm as the annealing temperature increased. On the other hand, the optical properties of as-deposited and annealed thin films were investigated by utilizing a UV-Visible spectrophotometer. The direct bandgap energies of as-deposited and annealed samples were estimated to be 2.34 eV, 2.31 eV, and 2.29 eV by using the well-known Tauc relation, respectively. The direct bandgap energy of thin films was also calculated using the derivative spectroscopy technique.

Plan-view TEM observation of a single-domain κ-Ga2O3 thin film grown on ε-GaFeO3 substrate using GaCl3 precursor by mist chemical vapor deposition

We demonstrated the growth of a single-domain κ-Ga2O3 thin film on ε-GaFeO3 by using an organic-free compound as a precursor for mist chemical vapor deposition. X-ray diffraction analysis revealed that an 86 nm thick κ-Ga2O3 thin film was grown almost coherently with slight lattice relaxation. The surface morphology of the κ-Ga2O3 thin film exhibited a step-terrace structure without island growth. Furthermore, plan-view TEM observations revealed that the κ-Ga2O3 thin film grown on ε-GaFeO3 had a single domain, whereas the previously reported κ-Ga2O3 thin film grown on AlN template had a domain structure.

Synthesis of n-type ZrO2 doped ε-Ga2O3 thin films by PLD and fabrication of Schottky diode

Tin-assisted pure phase n-type ZrO2-doped ε-Ga2O3 films were synthesized by pulsed laser deposition (PLD) and deposited on (0001) epi-GaN/sapphire substrates. The characterization of n-type ZrO2-doped ε-Ga2O3 thin films and the electrical properties of SBD based on that film were investigated in details. From XRD, the pure Zr-doped ε-Ga2O3 without diffraction peaks of zirconia suggested the formation of ε-(ZrxGa1−x)2O3 solid solution. The surface morphology and chemical content of the ε-Ga2O3 thin film were studied by AFM and XPS. The electrical resistivity and related free carrier concentration at room temperature were measured to be 108 Ω·cm and 5.5 × 1015 cm−3, respectively, and mobility up to 10.3 cm2/V·s. The Schottky barrier diode possessed a rectification ratio up to 106~107, breakdown voltage of 392 V, and the interface states density from 2.4 × 1013 cm-2 eV-1 to 6.4 × 1014 cm-2 eV-1 with the trap energy level from 0.89 eV to 0.94 eV below the bottom of the conduction band.

Impact of surface morphology and thickness of tin selenide thin films on their optical properties

Thin tin selenide (SnSe) films were synthesized on polyamide sheets via the two-stage adsorption/diffusion method. The surface morphology and chemical composition of the hereby obtained thin film were characterized by energy-dispersive spectroscopy, field-emission scanning electron microscopy, X-ray diffraction, and X-ray photoemission spectroscopy techniques. The X-ray diffraction analysis showed that the obtained films are chemically close to tin selenide with three orthorhombic phases. A systematic investigation was carried out to understand the factors of the next stage process, the influence of conditions on the structure, the surface morphology of SnSe thin films, and their thickness. It was found that the concentration of tin(II) precursor solution, its pH value, and temperature led to the creation of films of various thickness and surfaces with different features. The SnSe films consisted of nanoscale ∼40 nm size grains, which in turn were combined into agglomerates of up to 100 nm to 3 µm. The stoichiometric ratios of tin and selenium in SnSe films were also dependent on the next-stage conditions of the synthesis process. The thickness of the SnSe films and the size of the crystallites of which they are composed have a decisive influence on the optical properties of these layers and the band gap of which varied in the range of 1.75–1.24 eV.

Local structure and structural properties of vanadium oxide thin films prepared by radio-frequency reactive magnetron sputtering at various oxygen flow rate

In this work, vanadium oxide thin films were prepared by using radio frequency reactive magnetron sputtering with vanadium metal target. The effect of O2 flow rate was investigated in terms of vanadium oxide thin films by varying O2/Ar flow rate at 1/20, 2/20, 3/20, 4/20, 5/20, 6/20 (in sccm unit) with fixed RF power at 200 W and sputtering time at 80 minutes. The surface morphology and crystal structure of V2O5 thin films were investigated by scanning electron microscope (SEM), atomic force microscope (AFM), and X-Ray Diffractometer (XRD) respectively. The influence of the O2/Ar ratio on a local structure of vanadium oxide thin films was studied by the Synchrotron x-ray absorption spectroscopy (XAS) technique. The oxidation states of vanadium oxide thin films were measured at V K-edge by the x-ray absorption near-edge structure (XANES). The results of XANES spectra at the V K-edge showed that the prepared films under the O2/Ar flow rate at 1/20 sccm contained the vanadium with the oxidation states of V3+ and V5+ while the others contained only V5+. This is because the higher O2/Ar flow rate possibly causes an increase in energy flux at the substrate and the 1s→3d transition peak’s intensity, which could lead to a higher deposition rate. To achieve the desired V2O5 structure, the gas flow rate could be adjusted properly. The evolution of the local structure around V atoms was studied using the extended x-ray absorption fine structure (EXAFS) which supported the XANES results indicating that the structural environment around V atoms is in good agreement with the V2O5 orthorhombic structure. Finally, XANES and EXAFS fitting results confirmed that the O2 flow rate affected the local structure of vanadium oxide thin films.

Effect of 2 MeV W+ ion irradiation on the surface morphology of Sc:In:C and Zr:In:C thin films

In this work, a comparative study of surface morphology and elemental distribution of thin films of the M:In:C (with M = Sc or Zr) ternary composites irradiated with 2 MeV W ions with fluences 10 cm and 10 cm was carried out. The films were prepared by ion beam sputtering of the M, In and C targets followed by thermal annealing in a high vacuum. The surface morphology was monitored by Atomic Force Microscopy (AFM), and the elemental composition by Rutherford Backscattering Spectroscopy (RBS) in the regime of elastic scattering (2000 keV He ions energy) and nuclear resonant scattering (3046 and 4280 keV He ions for O and C resonances, respectively). It has been shown that both deployed modifications (thermal annealing and ion beam irradiation) seriously affect the surface morphology and the elemental distribution of both composites. It turned out that the main reason for the changes is a decrease in the content of indium in the composites, which after irradiation with a high fluence of 10 cm decreased to almost zero. It also turned out that the morphological changes take place differently in the inspected composites - more significantly in Zr:In:C, less in Sc:In:C.

Experimental and In Silico studies on optical properties of new thiadiazole tetrasubstituted metal-free and zinc phthalocyanine compounds

In this study, 2-amino-5-phenyl-1,3,4-thiadiazole substituted metal-free phthalocyanine (H2Pc) was synthesized by tetramerization reaction of the phthalonitrile derivative. The synthesized compound was characterized by IR, UV–Vis, 1H NMR, MS spectroscopy and elemental analysis. To determine the potential of the synthesized phthalocyanines to be used in optical applications (thiadiazole substituted metal-free and zinc(II) derivatives), photoluminescence and fluorescence properties of compounds were studied. In addition, the powder and thin film surface morphology of these compounds were examined by scanning electron microscope (SEM). The electronic features (chemical hardness, electron affinity, electronegativity) and frontier orbital energy levels (HOMO-LUMO) were computed using density functional theory. The HOMO-LUMO energies of (H2Pc) and zinc(II) phthalocyanine (ZnPc) were acquired close to each other. The spectroscopic studies showed that the UV–visible spectra obtained using time-dependent density functional theory (TDDFT) was compatible with the experimental UV–visible study. The nonlinear optical (NLO) results indicated that the NLO properties of H2Pc are slightly better than ZnPc.