As-deposited Thin Films Research Articles

Transformation kinetics for low temperature post-deposition crystallization of TiO2 thin films prepared via atomic layer deposition from TDMAT and water

Background: We report on the fundamental crystallization kinetics of atomic layer deposited (ALD) TiO2 thin films undergoing a post-deposition anneal (PDA) at low temperatures to probe differences in the as-deposited film microstructure. Methods: The system of study is ALD TiO2 thin films prepared from tetrakis(dimethylamino)titanium(IV) (TDMAT) and water at 120 °C, 140 °C and 160 °C followed by ex situ low temperature annealing at temperatures ranging from 140 °C to 220 °C. All as-deposited TiO2 thin films are amorphous by X-ray diffraction (XRD). Post-deposition annealing (PDA) produces large grain anatase crystals, confirmed by XRD and top-view scanning electron microscopy (SEM). A detailed SEM study is performed to quantify the nucleation and growth kinetics by fitting microstructural data to the Johnson-Mehl-Avrami-Kolmogorov (JMAK) equation. Finally, a time-temperature-transformation (TTT) diagram is constructed to summarize the differences in crystallization behavior at different ALD deposition temperatures. Results and Conclusions: Fitting microstructural data to the JMAK equation reveals an Avrami exponent close to 3 with continuous nucleation, suggesting two-dimensional, plate-like crystal growth. Applying an Arrhenius relationship to the phase transformation data, the combined activation energy for nucleation and growth is found to be 1.40–1.58 eV atom-1. Nucleation rates are determined, and an Arrhenius relationship is used to calculate the critical Gibbs free energy for nucleation (~1.3-1.4 eV atom-1). As such, nucleation is the rate-limiting step for the amorphous to anatase phase transformation. ALD growth temperature is found to dictate film microstructure with lower deposition temperatures reducing the nucleation rate and leading to larger grain sizes irrespective of PDA conditions. The nucleation rate pre-exponential frequency factor increases with increasing deposition temperature, thereby increasing the likelihood for nucleation. Interestingly, it is this difference in the vibrational modes of the amorphous structure, as indicated by the variation in the nucleation rate pre-exponential frequency factor, that alters the phase transformation rates and not a change in the activation energies for the transformation.

On the presence of oxyphosphorus bonds in TOPCon solar cell polycrystalline silicon films

The presence of silicon oxyphosphorus bonds in the heavily phosphorus (P)-doped n+-type polycrystalline silicon film (n+-poly Si) of TOPCon solar cell has been mainly revealed through a depth-profile X-ray photoelectron spectroscopy (XPS) characterization of chemical components. X-ray diffraction (XRD) pattern is applied to the verification of recrystallized phases in the n+-poly Si film, while high-resolution transmission electron microscopy (HR-TEM) with energy dispersive X-ray (EDX) pattern is used for distinguishing the crystallinity and the elemental segregation. The test sample is of a typical rear passivation contact stacks of c-Si/SiOx/n+-poly Si/SiO2, in which the n+-poly Si layer is heavily phosphorus-doped by ion implantation of as-deposited intrinsic thin film through low-pressure chemical vapor deposition (LPCVD) and recrystallization at 900 °C afterward. In the whole n+-poly Si layer, XPS P 2p electronic states at 129.8, 133.4 and 136.8 eV have been detected and assigned to be Si–P (or P–P), O–P and P–O–P bonds, respectively. In addition, the thermodynamic functions, such as the Gibbs free energy and mole formation energy of likely chemical bonds under the lowest energy as well as temperature-composition fraction (T-CF) phase diagram, are also implemented in the verification of the derivatives of phosphorus oxides.

Studying spectroscopic, cyclic voltammetry, and electrical properties of novel 4-amino antipyrine derivative for photonic applications

The present work aims to synthesize a new antipyrine derivative and then study its optical properties in the form of thin films with the aim of using the obtained results in the fabrication and designing of new optoelectronic devices. A N1,N3-bis(1,5-dimethyl-3-oxo-2-phenyl-2,3-dihydro-1H-pyrazol-4-yl)malonamide, dpdp novel organic compound has been successfully synthesized in dimethylformamide (DMF) medium by the chemical reaction between 4-aminoantipyrine and malonyl chloride. The obtained dpdp compound is characterized quantitatively and qualitatively by using micro elemental analysis, FTIR spectroscopy, 1H– & 13C–NMR, and thermogravimetric measurements. Two steps weight loss of 84 % (calcd. mass loss 37.25 %) is recorded in the temperature range of 25 °C to 800 °C. Thin films of the novel organic dpdp were successfully grown by the thermal evaporation technique. FSEM images show the surface topology of the as-deposited thin film which is characterized by high quality, continuous, and crystalline granular surface with an average particle size of 70 nm. The cyclic voltammetric analysis showed that the energy difference between the HOMO and LUMO equals 2.43 eV. The calculated values of the optical band gap transitions deduced from the diffuse reflectance spectra are found to be 2.27 eV, and 3.44 eV for the powder and the as-deposited dpdp thin films, respectively. The photoluminescence spectra analysis showed that the as-deposited film dpdp is characterized by a main green peak centered at 530 nm. The optical transflection spectra showed that the calculated values of the indirect optical band gap transitions are found to be 3.53 eV for the as-deposited thin film which slightly increased to 3.63 eV after annealing at 373 K and 423 K for 4 h. Spectral variations of the refractive index and the specific polarizability showed one peak around 400 nm which fades by annealing treatment at 373 K and 423 K. The dc electrical resistivity activation energy of the free charge carriers was estimated.

Investigation of the Microstructure, Optical, Electrical and Nanomechanical Properties of ZnOx Thin Films Deposited by Magnetron Sputtering.

The paper presents the results of an investigation of the influence of technological parameters on the microstructure, optical, electrical and nanomechanical properties of zinc oxide coatings prepared using the pulsed reactive magnetron sputtering method. Three sets of ZnOx thin films were deposited in metallic, shallow dielectric and deep dielectric sputtering modes. Structural investigations showed that thin films deposited in the metallic mode were nanocrystalline with mixed hexagonal phases of metallic zinc and zinc oxide with crystallite size of 9.1 and 6.0 nm, respectively. On the contrary, the coatings deposited in both dielectric modes had a nanocrystalline ZnO structure with an average crystallite size smaller than 10 nm. Moreover, coatings deposited in the dielectric modes had an average transmission of 84% in the visible wavelength range, while thin films deposited in the metallic mode were opaque. Measurements of electrical properties revealed that the resistivity of as-deposited thin films was in the range of 10−4 Ωcm to 108 Ωcm. Coatings deposited in the metallic mode had the lowest hardness of 2.2 GPa and the worst scratch resistance among all sputtered coatings, whereas the best mechanical properties were obtained for the film sputtered in the deep dielectric mode. The obtained hardness of 11.5 GPa is one of the highest reported to date in the literature for undoped ZnO.

Annealing Effects on SnO2 Thin Film for H2 Gas Sensing.

Hydrogen (H2) is attracting attention as a renewable energy source in various fields. However, H2 has a potential danger that it can easily cause a backfire or explosion owing to minor external factors. Therefore, H2 gas monitoring is significant, particularly near the lower explosive limit. Herein, tin dioxide (SnO2) thin films were annealed at different times. The as-obtained thin films were used as sensing materials for H2 gas. Here, the performance of the SnO2 thin film sensor was studied to understand the effect of annealing and operating temperature conditions of gas sensors to further improve their performance. The gas sensing properties exhibited by the 3-h annealed SnO2 thin film showed the highest response compared to the unannealed SnO2 thin film by approximately 1.5 times. The as-deposited SnO2 thin film showed a high response and fast response time to 5% H2 gas at 300 °C of 257.34% and 3 s, respectively.

Insight into the photoinduced phenomena in ternary Ge-Sb-Se sputtered thin films

The kinetics of photoinduced changes, namely, photobleaching and photodarkening in sputtered ternary Ge 29 Sb 8 Se 63 thin films, was studied. The study of time evolution of the absorption coefficient Δ α ( t ) upon room-temperature near-bandgap irradiation revealed several types of photoinduced effects. The as-deposited films exhibited a fast photodarkening followed by a dominative photobleaching process. Annealed thin films were found to undergo photodarkening only. The local structure studied by Raman scattering spectroscopy showed significant structural changes upon thermal annealing, which are presumably responsible for a transition from the photobleaching observed in as-deposited and reversible photodarkening in annealed thin films. Moreover, a transient photodarkening process was observed in both as-deposited and annealed thin films. The influence of the initial film thickness and laser optical intensity on the kinetics of photoinduced changes is discussed.

Comparative Study of Structural and Mechanical Properties of as Deposited and Shock Wave Exposed NiW Nano Structured Thin Films

The current work describes the effect of shock wave exposure on electroplated NiW thin films. NiW thin films were deposited through electrodeposition process by varying the bath temperatures (35°C and 70°C) at constant current density of 1A/dm2. The deposited NiW thin films were exposed to shock waves with varying Mach numbers of 1.13 and 2.33 using an in-house shock wave tube facility. The as-deposited and shock wave-exposed NiW thin films were characterized by XRD, FESEM, EDS, and EIS to reveal its structural and mechanical properties. The XRD results disclose the stable cubic structural phase of as deposited and shock wave exposed NiW thin films with average crystallite size varying between 5 nm to 17nm. The elemental composition of as-deposited and shock-wave exposed films are similar as confirmed in the EDS analysis. This henceforth represents the stability of nanostructured NiW film in terms of compositional and structural aspect. Morphological analysis through FESEM shows that the exposed thin film is defect free due to the impact of shock waves. Furthermore, corrosion resistance is observed to enhance ten times in shock-wave exposed thin film than as-deposited thin film for higher mach number (Pressure ~63 bar). Similarly, corrosion resistance for low mach number (pressure ~13 bar) increases by three times of as deposited film according to the EIS analysis. Therefore, the structural, morphological and corrosion properties were enhanced upon surface treatment by shock wave exposure. NiW thin films with enhanced mechanical properties such as low corrosion rate, high corrosion resistance is used in various industrial applications like defense applications, aircraft, and marine applications.

Annealing effects on epitaxial (K,Na)NbO3 thin films grown on Si substrates

Epitaxial (K,Na)NbO3 (KNN) thin films were deposited on (001)SrRuO3/Pt/ZrO2/Si substrates by RF magnetron sputtering, and post-annealing effects on the as-deposited epitaxial KNN thin films were investigated. According to the findings, by annealing, the crystal system of these thin films changes from a tetragonal to an orthorhombic system because of the release of internal stress. The asymmetry of polarization–electric field hysteresis loops along the electric field changes from a positive to a negative side by annealing. This means that stable spontaneous polarization P s changes from the upward to downward direction with an increase in the number of A-site vacancies. In addition, the displacement–electric field curves of epitaxial KNN/Si unimorph cantilevers exhibit asymmetric behaviors. A relatively high converse piezoelectric coefficient ∣e 31,f ∣ = 6.4 C m−2 is obtained for 5 h annealed epitaxial KNN thin films.

In situ high-temperature X-ray diffraction measurements of Pb(Zr0.58Ti0.42)O3 epitaxial thin films grown on Si substrates

Pb(Zr,Ti)O3 (PZT) thin films with rhombohedral composition of Zr/Ti = 58/42 were epitaxially grown on SrRuO3/Pt/ZrO2/Si(001) substrates by radio frequency (RF) magnetron sputtering and their temperature dependence was investigated. In situ high-temperature X-ray diffraction measurements were conducted by the synchrotron radiation X-ray (SPring-8). The as-deposited PZT thin film showed a tetragonal structure due to a clamping effect from substrates. On heating, the diffraction spot was split into two peaks from 600 °C to 750 °C, while the split peaks were maintained on cooling to room temperature. This result indicates that tetragonal and cubic structures coexisted above 600 °C, whereas cubic to rhombohedral phase transition occurred on cooling. After the high-temperature measurement, the PZT thin films showed large voltage dependence of the converse piezoelectric coefficients (∣e 31, f ∣) due to the drastic change of the crystallographic structure by the high-temperature treatment.

Large shift in surface plasmon resonance wavelength with growth of embedded Au nanoparticles in fullerene C60 by Collision Cascades

We report a 220 keV Ag ion beam irradiation-induced modifications of thin films of fullerene C60 containing gold (Au) nanoparticles. Nanocomposite thin films of Au-C60 were synthesized using a thermal co-deposition technique on a glass substrate. The as-deposited (pristine) thin films were irradiated by 220 keV Ag ion beam at different fluences ranging from 1 × 1013 ions/cm2 to 3 × 1016 ions/cm2 utilizing a low energy ion accelerator. The optical properties of pristine and irradiated thin films of Au-C60 were investigated using UV–visible spectroscopy. A redshift in the Surface Plasmon Resonance (SPR) wavelength from ~ 598–775 nm was obtained with increasing fluence up to 1 × 1014 ions/cm2, which indicated the growth of Au nanoparticles in the fullerene matrix due to ion irradiation. It was further confirmed by High-Resolution Transmission Electron Microscopy (HRTEM). With further increase in fluence, a blue shift from ~ 775–570 nm was obtained at a fluence of 1 × 1016 ions/cm2. The transformation of fullerene C60 into amorphous carbon (a:C) with increasing fluence of Ag ion beam was the main cause of this blue shift which was further confirmed by Raman spectroscopy. An increase in surface grain size with ion fluence was observed by Atomic Force Microscopy (AFM) and Field Emission Scanning Electron Microscope (FESEM). The X-ray Photoelectron Spectroscopy (XPS) measurements were used for the chemical state analysis of the nanocomposite thin films before and after irradiation. The current-voltage measurements confirm the increase in the conductivity of the nanocomposite films with the fluence due to its transformation in carbon at higher fluences. The control on the size of Au nanoparticles and tuning of SPR wavelength by low energy ion irradiation may enhance the applicability of Au-C60 nanocomposite in organic solar cell.

Next-gen approach to the combined micro/macro-scopic measurements of crystal growth in chalcogenide thin films: The case of Se90Te10

Crystal growth in 1 µm Se90Te10 thin films deposited on a variety of substrates was studied by means of a novel combination of direct microscopic and calorimetric measurements. Differential scanning calorimetry (DSC) was used to explore the macroscopic manifestation of the crystal growth in as-deposited Se90Te10 thin films, revealing the native-like crystal growth behavior (very close to that of the bulk glass) in the films deposited on the polymeric foil. The optical microscopy determined the following sequence for the crystal growth rates ur in the thin films deposited on different substrates: urwhite glass> urSiO2 glass> >urKapton. This finding is perfectly consistent with the calorimetric data, and can be explained by the combined influences of the Na+ ions migrating from the white glass substrate to the thin film/substrate interface, and by the compressive stresses arising from the large difference between the thermal expansion coefficients of Se90Te10 and the inorganic glasses. Conformation of the calorimetric and microscopic data was validated by the description of both datasets in terms of a single set of parametrized equations based on the combination of the temperature-resolved screw-dislocation growth model and the macroscopic nucleation-growth model. The novel approach to the crystal growth research in chalcogenide thin films was introduced, demonstrating its unprecedented accuracy, robustness and overall comprehension. All major aspects of this novel approach were discussed in detail, including the necessity to consider not only the substrate properties but also the associated process of structural relaxation that may significantly alter the crystal growth near glass transition.

Diffusion behaviors of Sn dopant in ITO films upon supercritical CO2 treatment and annealing

Indium Tin Oxide (ITO) thin films have been extensively studied for their excellent photoelectric performance. Nevertheless, the diffusion mechanism of doped-tin in ITO thin film is not sufficiently illuminated to date. Herein, the diffusion behaviors of Sn dopant in ITO films fabricated by RF-sputtering were investigated. As-deposited ITO thin films were treated by supercritical CO2 (SCCO2) fluid with aqua ammonia, then they were annealed at different temperatures. X-ray diffraction patterns (XRD) showed that the crystallization of ITO films occurred upon annealing above 300 °C, which resulted in the higher mobility of electron carriers. Relatively lower electron carrier concentrations were found for the ITO films after SCCO2 treatment and successive annealing at temperatures of 500 and 600 °C. X-ray photoelectron spectroscopy (XPS) analysis revealed that the content of tin element near the surface of ITO thin films can be reduced by SCCO2 fluid treatment. Subsequently, the annealing process results in the diffusion of the tin element to the sub-surface region of the films at different levels depending on the annealing temperature. The present work provides direct evidence for bleaching of tin dopant in the sub-surface region of ITO films by SCCO2 treatments and diffusion of tin from deeper regions to the sub-surface region of the ITO films upon annealing.

High-Capacity Cathodes for All-Solid-State Thin-Film Batteries

Lithium-ion batteries (LIBs) are critically important rechargeable energy storage devices, finding widespread application in consumer electronics and electric vehicles. However, safety issues associated with their flammability impede their development for many applications. As a fully solid-state device, the thin film battery (TFB) is a compelling candidate for advanced microscale applications, including wearable devices, smart ID cards, and microelectromechanical systems (MEMS). A typical TFB design consists of solid thin films of crystalline cathode, amorphous LiPON electrolyte, Li metal anode and current collectors supported on a rigid substrate. Polycrystalline cathodes are often employed, such as LiCoO2, Li2Mn2O4, LiNiO2, V2O5, etc., because they provide high specific capacity and good reversibility. However, these cathodes require thermal treatment to generate the crystalline microstructure for optimal electrochemical performance, demanding substrates that are stable to several hundreds of degrees Celsius. The industry is interested in lower-cost, flexible all-solid-state thin-film batteries that can be readily integrated into a wide range of applications, including wearable devices. Thus, there is strong demand for thin film cathodes that can be processed at low temperatures.Herein, we report a new amorphous inorganic thin-film cathode material, which is a solid state composite of Li2RuO3 and LiCoO2. (LRCO). Without any post-deposition annealing steps, as-deposited LRCO thin films possess a high discharge capacity of over 110 µAh cm-2 µm-1 at 0.3 C and capacity retention over 92% after 150 cycles owing to both cationic and anionic (oxygen oxidation) redox processes, which is competitive with conventional polycrystalline thin-film cathodes. The surface of LRCO cathode is smooth and isotropic, leading to uniform Li ion transport and thereby reducing the possibility of short-circuiting. More importantly, the entire preparation process is conducted at room temperature, enabling wider substrate options for TFBs, such as Kapton® films, polyethylene terephthalate (PET) films, or even paper sheets. Using PET plastic sheets to support LRCO TFBs; a specific capacity of 101 µAh cm-2 µm-1 at 0.3 C and capacity retention of 97.5% after 120 cycles was achieved, even when the substrate was mechanically bent (flexed).

Deposition and characterization of silicon thin film on stainless steel by electron beam evaporation

Silicon (Si) is a promising material as anode electrode because of its high theoretical capacity of 3579 mAh g−1 and low electrode potential (< 0.4 V vs. Li/Li+). In this paper, the Si thin film electrodes were fabricated by using electron beam evaporation on the stainless steel (SS) foil at room temperature. The structural and electrochemical characterization were investigated for the Si thin film electrodes before and after annealing at 700 ˚C. X-ray photoelectron spectroscopy analysis revealed that the annealed film layer consisted of SiOx containing about 30 at.% oxygen. The annealed Si thin film electrode resulted in improved electrochemical performance compared to as-deposited Si thin film electrode. The Si thin film electrode after annealing exhibited an initial discharge capacity of 2270 mAh g−1, and sustained excellent cycle stability with retention capacity about 95 % for 100 cycles at 0.5 C-rate. The improvement in cyclability for the annealed Si thin film electrode can be attributed to the enhanced adhesion of Si thin film to SS substrate through interdiffuion at the Si/SS interface owing to the post-annealing process.

Resistive switching properties of amorphous Sm2Ti2O7 thin film prepared by RF sputtering for RRAM applications

The resistive switching (RS) characteristics of amorphous Sm2Ti2O7 thin films prepared by using RF sputtering were investigated and the effect of post-metallization annealing (PMA) on the RS properties were analysed. Comparison of as-deposited Sm2Ti2O7 thin film device and the device after PMA treatment, the latter exhibits better RS properties, including more uniform set voltages, switching cycle times and higher Ron/Roff ratio. The prepared samples all revealed bipolar resistive switching (BRS) behaviour. The results indicated that the conductive mechanism in terms of the concentration of oxygen vacancies can be controlled by different deposition atmosphere (Ar/O2) ratio and film thickness. Additionally, the resistive switching properties can be enhanced by PMA treatment due to the formation of AlOx interface layer, which prevents the oxygen ions from out-diffusion through the boundaries. At the PMA temperature of 350 °C, the two resistance states can be distinguished in a range of> 10 over 8099 switching cycles along with a retention of 104 s at room temperature and 85ºC, showing promise for non-volatile memory applications.

Effects of annealing on SnS films produced by chemical bath deposition (CBD)

Tin sulfide (SnS) thin films were produced on glass substrates at 65 °C by chemical bath deposition (CBD). Two of the obtained five identical films were annealed in an air atmosphere while the other two were annealed in a nitrogen atmosphere at different temperatures. The effects of annealing (at 150 °C and 250 °C in air and nitrogen atmospheres) on the optical, structural, and electrical properties of the films were investigated by UV-visible spectrophotometer, x-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), and Hall-effect measurement. The energy band gap of as-deposited SnS thin film was determined to be 1.16 eV, and it was observed to change with annealing. All of the as-deposited and annealed SnS films had orthorhombic structures. The optical phonon modes to orthorhombic SnS phases were determined by Raman shifts. The carrier type of all SnS films was identified as p-type using Hall measurement, and the changing carrier concentration, mobility, and resistivity values of the films were investigated depending on annealing conditions. The p-type SnS film can be used as an alternative material for the absorber layer in p-n heterojunction solar cell applications.

Ohmic-Schottky conversion of ZnO/metal contact modulated by a plasma surface treatment method

Herein, we present a systematical investigation with regard to the Ar/N2/O2 plasma surface treatments on the ZnO thin films prepared by a radio frequency plasma-assisted molecular beam epitaxy (RF MBE) technique. The as-deposited ZnO thin films are exposed to the Ar, N2 and O2 plasma atmospheres under different RF powers. The conductivity and the surface morphology of the post-treated ZnO thin films are strongly depending on the treatment species and the RF powers. Higher RF power results in lower resistance and reduces the grain boundaries of the surface. Indium and gold metals are designed as the Ohmic and Schottky contact electrodes, respectively. The ZnO/Au contacts based on both pre-treated films and Ar/N2 plasma-treated films show obvious Ohmic contact behaviors. However, In/ZnO/Au the devices fabricated on the ZnO thin film which exposes to the O2 plasma show distinct rectified behavior, indicating the conversion of ZnO/Au contact from Ohmic type to Schottky type. The O2 plasma treatment may play two key roles within the contact conversion: 1, removing the surface contaminants such as carbon, absorbed oxygen and hydroxide; 2, repairing the defects (Vo), thus reducing the near surface donor density and defect assisted hopping transportation.

Improved linear and nonlinear optical properties of PbS thin films synthesized by spray pyrolysis technique for optoelectronics: An effect of Gd3+ doping concentrations

In the present article, the pure PbS and different concentrations of Gd doped PbS (Gd:PbS) films were developed using the spray pyrolysis route by growing thin films on the glass substrate. The estimated crystallite sizes were found from 15.5 to 20.8 nm for as-deposited films. The spherical shape morphology of grains was observed by FESEM. The obtained average grain sizes varied from 52.8 to 108.2 nm were obtained from the grain size distributions for 0.0, 0.5, 1.5, and 2.5 wt % Gd: PbS films, respectively. Extinction coefficients of as-deposited films were measured from 0.04 to 0.12 in the range of wavelength 200–2500 nm. Refractive indices of films were obtained from 5.4 to 1.22 in range of 200–2500 nm wavelength. The band gaps of 2.75, 2.64, 2.45, and 3.10 eV for 0.0, 0.5, 1.0 and 2.5 wt % Gd thin films were estimated using Tauc's relation respectively. The values of the dielectric constant, dielectric loss, and optical conductivity were recorded in the range of 1.32–29.6, 0.30–0.61, and 2.34 × 1014–3.08 × 1013 between 200 and 2500 nm wavelengths for as-deposited thin films respectively. The optimum values of linear susceptibility, non-linear susceptibility and refractive index were recorded in the range of 1.23–2.93, 5.21 × 10−10 - 120 × 10−10, 3.54 × 10−9 – 74.2 × 10−9 (esu) between 1.46 and 0.52 eV respectively for as-deposited thin films. The Gd: PbS thin films improve the physical properties and therefore, it becomes suitable candidature for the applications in optoelectronic devices.

Spectroscopic and Physicochemical Studies on 1,2,4-Triazine Derivative

A novel 5-(5-Bromo-2-hydroxybenzylidene)-6-oxo-3-phenyl-5,6-dihydro-1,2,4-triazine-2(1H)-carbothioamide (4) “compound 4” was synthesized. The chemical structure of compound 4 was confirmed with spectroscopic techniques. Thermal analysis (TGA/dTGA) studies were conducted for identifying the kinetic thermodynamic parameters and the thermal stability of the synthesized compound 4. Cyclic voltammetric studies were performed for recognizing electrochemical characteristics of the synthesized compound 4. The calculated highest occupied molecular orbital (HOMO), lowest unoccupied molecular orbital (LUMO), and the band gap were found to be −3.61, −5.32, and 1.97 eV, respectively. Using a diffused reflectance spectroscopy (DRS) technique, the estimated values of the optical band transitions of compound 4 in powder form were found to be 2.07 and 2.67 eV. The structural properties of thermally evaporated compound 4 thin films were analyzed using field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), and Fourier transform infrared (FTIR) spectroscopy. It was found that compound 4 has a triclinic crystal structure. The optical transitions and the optical dispersion factors of compound 4 thin films were investigated using a UV-Vis spectroscopy technique. From the UV-Vis spectroscopy technique, Egind=3.6 V was estimated for both the as-deposited and annealed thin films. For the as-deposited film, there were two photoluminescence (PL) emission peaks centered at 473 and 490 nm with a shoulder at 422 nm. For the annealed film at 423 K, there were five PL emission peaks centered at 274, 416, 439, 464, and 707 nm with a shoulder at 548 nm. The dark electrical conduction of compound 4 thin film was through a thermally activated process with activation energy equaling 0.88 eV.

Control of Transfer Characteristics of Atomic Layer Deposited Al-Doped SnO2 Thin Film through a Post-Annealing Process

In this paper, changes in transfer characteristics for an Al-doped SnO2 thin film using the annealing process was studied. Generally, as-deposited SnO2 thin film has electrical properties similar to those of the conductor due to high carrier concentration. However, various electrical properties such as on/off current ratio could be obtained as Al was doped and the annealing process was performed in an air atmosphere. As a result of XPS analysis, it was confirmed that the concentration of oxygen vacancy concentration decreased when the Al-doped SnO2 thin film was annealed. Compared to the as-deposited Al-doped SnO2 thin film, the annealed Al-doped SnO2 thin film had superior channel characteristics because the oxygen vacancy concentration in the SnO2 thin film was lowered by the oxygen atom diffusion during the annealing process. This is due to the lower carrier concentration. As a result of analyzing the electrical properties of the annealed Al-doped SnO2 thin film, that film annealed at 500 °C, an on/off current ratio of 106 was obtained. And the field effect mobility was also 1.56 cm2 Vs−1.