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1

Comparison of electrical properties of CuO/n-Si contacts with Cu/n-Si

Özmenteş Reşit, Temirci Cabir

Materials Science Poland

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2020

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Vol. 38, No. 3

475--483

EN

In this study, CuO/n-Si/Al heterojunction contacts were fabricated by thermal evaporation technique. Electrical characteristics of the samples were investigated with the current-voltage (I-V), capacitance-voltage/frequency (C-V/f), and conductance-voltage (G/V) measurements at room temperature. Also, Cu/n-Si/Al Schottky contact was produced as a reference sample to investigate the electrical properties of the samples. The values of ideality factor (n), barrier height (φb) and series resistance (Rs) of the samples were calculated from the forward bias current-voltage (I-V) and reverse bias capacitance-voltage (C-V) characteristics. Also, for checking the consistency of the results, Cheung and Norde functions were used. The experimental result values of CuO/n-Si contact were compared with the values of the reference Cu/n-Si Schottky diode. It was observed that the values of the ideality factor and barrier height of the CuO/n-Si heterojunction were higher than those of the Cu/n-Si Schottky contact, while the series resistance was lower. Also, it has been observed that the value of capacitance decreased with increasing frequency and after a certain value of frequency it was almost constant. The ideality factor of CuO/n-Si/Al heterostructure is about 2.40 and so, it is not close to the ideal behavior.

2

Study of crystallographic, optical and sensing properties of Na2WO4 films deposited by thermal evaporation with several thickness

Abdallah B., Kakhia M., Abou Shaker S.

Materials Science Poland

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2019

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Vol. 37, No. 4

590--598

EN

Na2WO4 films have been grown at 400 °C using thermal evaporation technique. Their structural properties were characterized by XRD, while their chemical composition was verified by both EDX and X-ray photoelectron spectroscopy (XPS). The evolution of crystallinity was studied as a function of film thickness that ranged from 500 nm to 3000 nm. The grain size increased with increasing film thickness. The surface morphology of the prepared films was studied using scanning electron microscope (SEM) and atomic force microscopy (AFM). It has been observed that the average transmittance of samples in the visible and near infrared range has varied from 90 % to 78 % with the film thickness. The optical band gap of the Na2WO4 films varied from 3.8 eV to 4.1 eV. The crystalline size increased with increasing thickness and showed better sensing response to gases. Thus, this study confirmed the possibility of using Na2WO4 thick films as a sensor element for detection of ethanol (C2H5OH), acetone (C3H6O) methanol (CH3OH) and ammonia hydroxide (NH4OH) vapor at room temperature, where thicker films exhibited sensing properties with a maximum sensitivity at 25 °C in air, especially for NH4OH.

3

Structural and optical characterization of annealed As30Te60Ga10 thin films prepared by thermal evaporation technique

Abd-Elnaiem A. M., Mohamed M., Hassan R. M., Abdel-Rahim M. A., Abu-Sehly A. A., Hafiz M. M.

Materials Science Poland

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2018

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Vol. 36, No. 2

193--202

EN

Effect of annealing temperature on the structural and optical properties of As30Te60Ga10 thin film was studied using various techniques such as differential scanning calorimetry (DSC), X-ray diffraction (XRD) and scanning electron microscopy (SEM). The DSC analysis revealed that the As30Te60Ga10 glass has a single glass transition and crystallization peak while XRD results confirmed that the as-prepared and annealed films have crystalline nature. The coexistence of the crystalline phases in the investigated films could be attributed to the formation of orthorhombic As, hexagonal Ga7Te10, and monoclinic As2Te3 phases. It was found that the average crystallite size and optical parameters of the studied films depend on the annealing temperature. For example, the optical band gap decreased from 1.54 eV to 1.11 eV as the annealing temperature increased from 300 K to 433 K.

4

Morphological, optical and electrochromic properties of dry-lithiated nanostructured WO3 thin films

Madhuri K. V., Babu M. B.

Materials Science Poland

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2018

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Vol. 36, No. 2

341--347

EN

Tungsten trioxide (WO3) thin films were prepared by thermal evaporation technique on thoroughly cleaned glass substrates at high pressure of 133.322 mPa in presence of argon. The substrate temperature was maintained from 6 °C to 8 °C with the help of a cold jar. The deposited films were annealed at 400 °C in air for about 2 hours. The films were characterized in terms of their composition by X-ray photoelectron spectroscopy. Subsequently, the laboratory developed dry lithiation method was used to intercalate lithium atoms into as-deposited films in various proportions. With the amount of lithium content inserted into the film, the films showed coloration in visible and near infrared regions. The morphology, coloration efficiency and optical constants of annealed and lithiated films were calculated.

5

Influence of annealing temperature on the structural and optical properties of As30Te70 thin films

Abd-Elnaiem A. M., Mohamed M., Hassan R. M., Abu-Sehly A. A., Abdel-Rahim M. A, Hafiz M. M.

Materials Science Poland

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2017

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Vol. 35, No. 2

335--345

EN

Chalcogenide glasses have attracted much attention largely due to their interesting physical and chemical properties. Though few published articles exist on the As-Te system, little is known about the optical properties of eutectic or near eutectic composition of As-Te system upon heat treatment. Therefore, this paper reports the effects of annealing temperature on the structural and optical parameters of As30Te70 thin films. The bulk and thin films of 150 nm thick As30Te70 chalcogenide glasses were prepared by melt-quenching and thermal evaporation techniques, respectively. The glass transition and crystallization reactions of the bulk samples were investigated using differential scanning calorimetry (DSC). The influence of annealing temperature on the transformation of the crystal structure was studied by X-ray diffraction (XRD), while the surface morphology of the annealed samples was examined using scanning electron microscope (SEM). The optical band gap, refractive index and extinction coefficient were also calculated. The DSC scans showed that the melting temperature remains constant at 636.56 K. In addition, other characteristic temperatures such as the glass transition temperature, the onset crystallization temperature, and the crystallization peak temperature increase with increasing the heating rate. The crystalline phases for the as-prepared and annealed films consist of orthorhombic As, hexagonal Te, and monoclinic As2Te3 phases. Furthermore, the average crystallite size, strain, and dislocation density depend on the annealing temperature. The optical absorption results revealed that the investigated films have a direct transition, and their optical energy gap decreases from 1.82 eV to 1.49 eV as the annealing temperature increases up to 433 K. However, the refractive index, extinction coefficient, dielectric constant and the ratio of free carrier concentration to its effective mass, increase with increasing the annealing temperature.

6

Synthesis and characterization of polyimide thin films obtained by thermal evaporation and solid state reaction

Al-Ajaj I. A., Kareem A. A.

Materials Science Poland

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2016

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Vol. 34, No. 1

132--136

EN

In this research polyimide films were prepared by physical vapor deposition (PVD), using solid state reaction of pyromellitic dianhydride (PMDA) and p-phenylene diamine (PDA) to form poly(amic acid) (PAA) films. The resultant films were converted to polyimide by thermal treatment, usually below 300 °C. For this study, a FT-IR spectrometer has been used to measure the effect of imidization temperature on the chemical structure of the vapor-deposited thin films of aromatic PI. When temperature increased, an increase in all absorption peaks was observed. This suggests that residual PAA monomers continued to be converted into PI. The surface topology of the PI films obtained at imidization temperatures of 150, 200, 250 °C for 1 hour was further examined by using AFM atomic force microscopy. It can be clearly seen that the surface became rougher with increasing imidization temperature. The thermal stability of polyimide was also studied by using thermogravimetric analysis (TGA).

7

Researches of topography and optical properties of the thin films NiPc/PTCDA donor acceptor couple

Weszka J., Jarka P., Chwastek-Ogierman M., Hajduk B.

Journal of Achievements in Materials and Manufacturing Engineering

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2012

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Vol. 53, nr 2

81--88

EN

Purpose: The aim of this work consists of researches of surface topography and optical properties of organic thin films of NiPc : PTCDA blends deposited by thermal evaporation from one source. Thin films of organic materials are provided as donor/acceptor couple in heterojuction solar cells. Design/methodology/approach: Films consisting of NiPc and PTCDA mixture were deposited by thermal evaporation from one source. By using blends with different PTCDA to NiPc ratios and steering the temperature of the sources and hence deposition rate different properties of layers are obtained. Findings: Both the chemical composition and technological parameters of deposition process has appeared to influence on optical properties and surface morphology of thin films. These parameters were found to influence surface morphology and UV-Vis absorption spectra. Research limitations/implications: The paper shows the methodology of deposition NiPc/PTCDA donor/ acceptor blends and the influence of evaporation parameters on properties of thin films. That can be used for the research of the planar heterojunction solar cells based on NiPc/PTCDA heterojunction donor-acceptor couple active layers. Practical implications: Results of researches suggest that blends of NiPc and PTCDA can be useful materials in organic photovoltaic device. However right deposition parameters and the blends proportions determine the properties of NiPc/PTCDA donor/acceptor thin films. Originality/value: The goal of this paper is to definie the surface topography and optical properties of thin films NiPc/PTCDA blends prepared with different proportions of components and parameters of evaporation process.

8

Investigations of morphology and optical properties of thin films of TiOPc/PTCDA donor acceptor couple

Weszka J., Jarka P., Hajduk B., Chwastek-Ogierman M.

Journal of Achievements in Materials and Manufacturing Engineering

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2012

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Vol. 55, nr 2

396--402

EN

Purpose: The aim of this work is studying surface topography and optical properties of organic thin films of TiOPc and PTCDA blends deposited by thermal vacuum evaporation. Design/methodology/approach: Thin films of blends of organic materials are provided as donor/acceptor couples in bulk heterojunction based organic solar cells. Thin films of TiOPc - PTCDA mixture have been deposited by thermal vacuum evaporation from one source with various ratios of blends components and deposition rates used. Both the chemical composition and technological parameters of the deposition process have appeared to influence on optical properties, UV-Vis absorption spectra in particular, and surface morphology of the as-prepared thin films. The paper reveals the methodology of deposition thin films of TiPc-PTCDA donor/ acceptor blends and the influence of deposition parameters on their properties. Findings: Thin films of such blends can be used for the research on the planar heterojunction solar cells based on donor-acceptor couple active layers. Results of these investigations suggest that blends of TiOPc and PTCDA can be suitable materials for preparing organic photovoltaic devices. Research limitations/implications: Deposition parameters and proportions of the blend components used determine the properties of TiOPc/PTCDA thin films. Originality/value: The goal of this paper is also to define relations connecting the surface morphology and optical properties of thin films of TiOPc-PTCDA blend prepared with their composition and parameters of the evaporation process.