Thermal Co-evaporation Method Research Articles

Effect of indium doping on the optoelectronic properties of ZnSe films

Polycrystalline In:ZnSe films were prepared by the thermal co-evaporation method, where high purity ZnSe and In2Se3 powders are taken as source materials. Orderly change in the X-ray diffraction peak position and red shift in the optical absorption edge have confirmed the incorporation of the dopant in the system. Photoluminescence spectra showed that the doped system has a Zn vacancy, which is in line with energy dispersive spectroscopy measurements. The chemical state of the doped films i.e., Zn2+, In3+ and Se2− was analysed by Raman and X-ray photoelectron spectroscopy (XPS); XPS has also indicated the incorporation of oxygen in small fractions which improves the conductivity of the films. The electrical investigation has revealed that electrical properties altered by doping and majority charge carriers are electrons and carrier density is in the order of 1015 cm−3. Films with 15 at. % In exhibited good photoresponse in the visible range and suitable for photodetector applications.

Optical Properties of 1D ZnO/MoS\(_2\) Heterostructures Synthesized by Thermal Evaporation Method

MoS2 material attracts a great attention from researchers due to its graphene-like structure and the bandgap difference between its hexagonal monolayer and bulks. Recently, ZnO/MoS2 heterostructures have been received significant interest due to their distinguished properties. In this study, one-dimensional ZnO and ZnO/MoS2 heterostructures were successfully synthesized by a thermal co-evaporation method. Compare with ZnO, the band-to-band emission of ZnO/MoS2 heterostructures establishes a “blueshift” towards a shorter wavelength. It could be explained by the lattice strain in ZnO/MoS2 heterostructures due to the difference of primitive cell of ZnO and MoS2. Additionally, the quench in the visible region of the PL spectrum of ZnO/MoS2 heterostructures also explains the reduction of the defect in ZnO due to the presence of MoS2.

Achieving ultrahigh power factor in n-type Ag2Se thin films by carrier engineering

Ag2Se-based thermoelectric materials are attracting great attention because of their potential in fabricating high-performance miniature and wearable electronics. Here, an advanced thermal co-evaporation method is employed to fabricate high-performance Ag2Se thin films with controllable compositions. The atomic ratio Ag/Se of 2.06 can tune the carrier concentration to 1.4 × 1019 cm−3, leading to a power factor of 6.27 μW cm−1K2 at room temperature. As well, an annealing process further improves the electrical transport properties by increasing the carrier mobility while maintaining the carrier concentration. Microstructure analysis indicates that annealing can reduce dislocation defect density and Ag vacancy concentration, contributing to a high Seebeck coefficient, finally resulting in a high power factor of 20.51 μWcm−1K−2 at 393 K. Moreover, a thermoelectric device composed of 18 legs is fabricated by using the optimized Ag2Se thin film, which presents a maximum output voltage and power of ∼1.7 mV and ∼22 nW at the temperature difference of 50 K. These results demonstrate that a combination of compositional optimization and annealing condition manipulation is effective to boost the thermoelectric performance of Ag2Se thin films, showing great potentials in applying for wearable electronics.

Investigation on spectroscopic and electrical properties of p-Si/CdSxSe1−x (0≤ x ≤1) heterostructures for photodetector applications

CdSxSe1−x (0 ≤ x ≤ 1) films were deposited on p-Si via thermal co-evaporation method with CdS and CdSe as source materials. The heterostructures were studied for their structural, spectroscopic and electrical be�haviours by using X-ray diffraction, photoluminescence spectroscopy, low temperature Raman spectroscopy and I-V characterization. Systematic shift in the diffraction peak has confirmed the composition modulation and presence of mixed phase in the ternary CdSSe. Temperature dependent Raman study showed that longitudinal optical modes are shifted to higher wavenumber, which is ascribed to variation in strain and lattice constants with temperature. The diode parameters including ideality factor and barrier height were extracted by applying various models to the temperature dependent I-V measurements. The spectral re�sponse of p-Si/CdSxSe1−x (0 ≤ x ≤ 1) were analysed and the heterostructure with x = 0.2 showed high response confirming the device suitability of the heterostructures

Fabrication, micro-structure characteristics and transport properties of co-evaporated thin films of Bi2Te3 on AlN coated stainless steel foils

N-type bismuth telluride (Bi2Te3) thin films were prepared on an aluminum nitride (AlN)-coated stainless steel foil substrate to obtain optimal thermoelectric performance. The thermal co-evaporation method was adopted so that we could vary the thin film composition, enabling us to investigate the relationship between the film composition, microstructure, crystal preferred orientation and thermoelectric properties. The influence of the substrate temperature was also investigated by synthesizing two sets of thin film samples; in one set the substrate was kept at room temperature (RT) while in the other set the substrate was maintained at a high temperature, of 300 °C, during deposition. The samples deposited at RT were amorphous in the as-deposited state and therefore were annealed at 280 °C to promote crystallization and phase development. The electrical resistivity and Seebeck coefficient were measured and the results were interpreted. Both the transport properties and crystal structure were observed to be strongly affected by non-stoichiometry and the choice of substrate temperature. We observed columnar microstructures with hexagonal grains and a multi-oriented crystal structure for the thin films deposited at high substrate temperatures, whereas highly (00 l) textured thin films with columns consisting of in-plane layers were fabricated from the stoichiometric annealed thin film samples originally synthesized at RT. Special emphasis was placed on examining the nature of tellurium (Te) atom based structural defects and their influence on thin film properties. We report maximum power factor (PF) of 1.35 mW/m K2 for near-stoichiometric film deposited at high substrate temperature, which was the highest among all studied cases.

Fabrication of high-efficiency Cu2(Zn,Cd)SnS4 solar cells by a rubidium fluoride assisted co-evaporation/annealing method

CCZTS solar cells with high efficiency over 10.6% are fabricated by a Rb-assisted thermal co-evaporation method.

Structural, morphological and transport properties of Ni doped ZnO thin films deposited by thermal co-evaporation method

Defects and doping play an important role in determine the physical and/or chemical properties of semiconductor materials. In this study, thermoelectric performance of nickel doped zinc oxide (Ni doped ZnO) was investigated in order to obtain the optimal defects concentration. The Ni doped ZnO thin films were prepared using thermal co-evaporation technique. It is observed that all the obtained samples exhibited preferential orientation along (002), the increases of Ni contents leads to crystallinity enhancement and lower surface roughness. The morphological, compositional and topological results of the Ni doped ZnO thin films indicate that the increases of Ni contents to 0.91% leads to low surface roughness (5.4 nm). The samples demonstrated an electrons concentration of 1.5 × 1019 cm−3, Seebeck coefficient at 178 μV∙K−1 and an electrical conductivity of 3175 S∙m with a maximum power factor of 101 μW∙m−1 K−2. The doping technique used in this work, showed promising results in producing high thermoelectric performance.

Efficacy of ion irradiation in strengthening the surface plasmon resonance effect of Au nanoparticles

Au-Fullerene nanocomposite thin films synthesized by thermal co-evaporation method are irradiated by low energy (2.6 MeV) Ar ions at fluence ranging from 1 × 1014 ions-cm−2 to 3 × 1016 ions-cm−2. To avoid the retrogression of attributes of fullerene subjected to presence of Au, selected concentration and thickness of gold film is kept very small. UV–visible spectroscopy demonstrates the surface plasmon resonance (SPR) peak at 677 nm for the pristine film and at 590 nm after irradiation at fluence of 1 × 1014 ions-cm−2, displaying a shift of 87 nm towards lower side. This confirms that the refractive index of fullerene decreases as an influence of exposure to Ar beam irradiation. Shift in refractive index is explained on the basis of Mie theory which is established by the existence of D and G band after irradiation as displayed in the results of Raman Spectroscopy. A slight increase in the size of Au nanoparticles in irradiated films is observed which is illustrated by TEM images. Atomic Force Microscopy (AFM) images indicate the varying roughness of thin films after irradiation and morphology is determined by SEM images. I-V characterization shows the conductive behavior of Au-fullerene nanocomposite film before and after irradiation at different fluence. There are two phenomena occurring simultaneously with the increase in ion irradiation fluence; one is increase in the size of metal nanoparticle and another is transformation of fullerene in amorphous carbon. This leads to the change in the SPR position of metal fullerene nanocomposite thin film, making ion irradiation as an effective tool to enhance and optimize the optical properties of metal fullerene nanocomposite thin film.

Influence of annealing process on the stable luminous CsPbCl3 perovskite films by thermal evaporation

Inorganic perovskites (CsPbX3, X = Cl, Br and I) have aroused great interest due to their extraordinary optoelectronic properties. Despite their rapid progress, device performances are hindered by the instabilities of perovskites. Herein, we employed a thermal co-evaporation method to prepare stable and compact CsPbCl3 films. These films could maintain stability in ambient air for 12 months. The effect of annealing temperature and annealing time on the CsPbCl3 films were researched. Films had high crystallinity and luminescent intensity with 3 μm large grains at optimal annealing condition. This result provides an insightful understanding of annealing process on CsPbCl3 films, as well as to offer a valuable approach for the future of optoelectronic devices based on perovskite materials.

Spectroscopic and electrical analysis of vacuum co-evaporated CdxZn1-xTe thin films

Abstract CdxZn1-xTe (CZT) films with different compositions were grown by thermal co-evaporation method, in which cadmium telluride (CdTe) and zinc telluride (ZnTe) were used as the source materials. The structural, morphological and optical properties of the films were characterized by x-ray diffraction (XRD), UV–Visible spectroscopy, scanning electron microscopy (SEM), atomic force microscopy (AFM), photoluminescence (PL) and Raman spectroscopy. Detailed analysis has shown that films were having cubic phase with orientation along (111) plane and the optical band gap reduced from 2.17 to 1.53 eV when x was varied from 0 to 1. SEM micrographs confirmed the homogeneity of the films. Depending on the composition, Raman peaks of CZT samples were mixture of the fundamental modes of the CdTe and ZnTe and indicate “trigonal” lattice of Tellurium (Te). Analysis of PL spectra suggested tellurium as isoelectronic exciton traps, recombination of carriers in the surface traps and donor-acceptor pair present in the samples. Under electrical properties, p to n-type conversion was witnessed for x = 0.4 and above. Optical bad gap of about 1.60 eV with minimum Urbach energy (28.88 meV) and favourable electrical properties has led to conclude that CZT films with x = 0.8 may be suitable for solar cell absorber.

Enhancing Non-linear Response of Fullerene via Incorporation of Gold Nanoparticles

Bi-functional nanocomposite thin films of fullerene C60 and C70 containing Au NPs were synthesized using thermal co-evaporation method. Different atomic concentrations of Au metal varying from 5 to 35 at.% was chosen to get the Au NPs with different sizes in fullerene matrix. The thickness of films and metal concentration is confirmed by Rutherford backscattering spectroscopy (RBS). UV-visible spectrum shows the excitation of SPR band in all samples except for the lowest metal concentration which is ~ 5 at.% and SPR is red shifted with increasing concentration of Au. The shift in SPR position with increasing metal concentration for both Au-C60 and Au-C70 is nearly linear. X-ray diffraction spectroscopy indicates the formation of bigger size particles with increasing metal concentration in both the cases of Au-C60 and Au-C70, which is further confirmed by transmission electron microscopy results. Au-C60 and Au-C70 (could) be interesting nanocomposites for surface-enhanced Raman scattering studies.

Investigation of sequential thermal annealing effect on Cu-C70 nanocomposite thin film

Cu-C70 nanocomposite thin film is synthesized via thermal co-evaporation method. The atomic concentration of Cu in the thin film is found to be ~4.5 at.% using Rutherford backscattering spectroscopy. Sequential thermal annealing is performed in an inert atmosphere (in presence of Ar) at various temperatures. Surface plasmon resonance (SPR) is spotted at ~585 nm for the sample annealed at 300 °C and the SPR peak is shifted towards ~621 nm for the sample annealed at 400 °C. In order to determine the modifications arising in the structure of fullerene C70 matrix due to annealing, Raman spectroscopy is used. At the highest temperature of 400 °C, the high-intensity Raman active modes of fullerene C70 can still be observed which shows that fullerene C70 is not completely transformed into amorphous carbon upto this temperature. Transmission electron microscopy is performed to determine the size of particles which is obtained ~35 nm for the sample annealed at 400 °C. The red shift in SPR wavelength at 400 °C is ascribed to the growth of Cu nanoparticles.

Synthesis and characterization of Cu-C60 plasmonic nanocomposite

Plasmonic nanocomposite thin film containing Cu metal nanoparticles in fullerene C60 matrix is developed by thermal co-evaporation method on glass substrate. In order to excite the surface plasmon resonance (SPR), thermal annealing is performed from 100 °C to 400 °C on as-deposited thin film in an inert atmosphere (continuous flow of Ar gas) for 30 min. SPR is successfully generated at ∼694 nm for the film annealed at a temperature of 300 °C which is further blue shifted at ∼684 nm at a temperature of 400 °C. The film thickness and Cu metal atomic concentration is found to be ∼70 nm and ∼27 at.%, respectively using Rutherford Backscattering Spectroscopy. Raman spectroscopy is used to identify the structural changes occurring in fullerene C60 matrix with thermal annealing. The transformation of fullerene C60 into amorphous carbon is observed with increasing temperature. Transmission electron microscopy is used to confirm the growth of Cu nanoparticles with increasing temperature and particle size is found to be 27.9 nm for the film annealed at 400 °C. The modifications in surface morphology of annealed samples are studied by field emission electron microscope (FE-SEM) and atomic force microscope (AFM). The absence of Copper oxide in the annealed samples is confirmed by X-ray photoelectron spectroscopy. Current vs. voltage measurements are performed to quantify the increased conductivity of annealed samples.

Electronic excitation induced modifications of structural, electrical and optical properties of Cu-C60 nanocomposite thin films

High energy ion irradiation significantly affects the size and shape of nanoparticles in composites. Low concentration metal fraction embedded in fullerene matrix in form of nanocomposites was synthesized by thermal co-evaporation method. Swift heavy ion irradiation was performed with 120MeV Au ion beam on Cu-C60 nanocomposites at different fluences 1×1012, 3×1012, 6×1012, 1×1013 and 3×1013ions/cm2. Absorption spectra demonstrated that absorption intensity of nanocomposite thin film was increased whereas absorption modes of fullerene C60 were diminished with fluence. Rutherford backscattering spectroscopy was also performed to estimate the thickness of the film and atomic metal fraction in matrix and found to be 45nm and 3%, respectively. Transmission electron microscopy was performed for structural and particle size evaluation of Cu nanoparticles (NPs) in fullerene C60 matrix. A growth of Cu nanoparticles is observed at a fluence of 3×1013ions/cm2 with a bi-modal distribution in fullerene C60. Structural evolution of fullerene C60 matrix with increasing fluence of 120MeV Au ion beam is studied by Raman spectroscopy which shows the amorphization of matrix (fullerene C60) at lower fluence. The growth of Cu nanoparticles is explained using the phenomena of Ostwald ripening.

Thermoelectric Micro-Refrigerator Based on Bismuth/Antimony Telluride

Thermoelectric micro-coolers based on bismuth telluride (Bi2Te3) and antimony telluride (Sb2Te3) are important in many practical applications thanks to their compactness and fluid-free circulation. In this paper, we studied thermoelectric properties of bismuth/antimony telluride (Bi/SbTe) thin films prepared by the thermal co-evaporation method, which yielded among the best thermoelectric quality. Different co-evaporation conditions such as deposition flux ratio of materials and substrate temperature during deposition were investigated to optimize the thermoelectric figure␣of merit of these materials. Micron-size refrigerators were designed and fabricated using standard lithography and etching technique. A three-layer structure was introduced, including a p-type layer, an n-type layer and an aluminum layer. Next to the main cooler, a pair of smaller Bi/SbTe junctions was used as a thermocouple to directly measure electron temperature of the main device. Etching properties of the thermoelectric materials were investigated and optimized to support the fabrication process of the micro-refrigerator. We discuss our results and address possible applications.

Investigation on optical and photoluminescence properties of organic semiconductor Al-Alq3 thin films for organic light-emitting diodes application

The optical constants, photoluminescence properties, and resistivity of Al-Alq3 thin films prepared by the thermal co-evaporation method on a silicon substrate are studied with various Al fractions. A variable angle spectroscopic ellipsometry is employed to determine the optical constants in the wavelength from 300 to 1200 nm at incidence angles of 65°, 70°, and 75°, respectively. Both the refractive indices and extinction coefficient apparently increase with increasing Al fractions. The intensity of photoluminescence spectra gradually increases with decreasing Al fractions due to intrinsic energy level transition of Alq3 organic semiconductor in the ultraviolet wave band. The resistivity decreases from 42.1 to 3.36 Ω·cm with increasing Al fraction from 40% to 70%, resulting in a larger emission intensity in photoluminescence spectra for the 40% Al fraction sample.

Synthesis and characterizations of Au-C60 nanocomposite

Au-C60 nanocomposite thin film (Au nanoparticles embedded in fullerene C60 matrix) is synthesized by thermal co-evaporation method and subsequent thermal annealing from 150 °C to 300 °C. A very small concentration of Au (∼2 at.%) is chosen in order to minimize the deterioration of the physical and chemical properties of fullerene C60 due to the presence of metal. Spherical shaped Au nanoparticles with a diameter of 2.1 ± 0.04 nm are clearly seen in the TEM images of the nanocomposite annealed at 200 °C. A broad surface plasmon resonance peak at ∼581 nm emerges in UV-visible absorption spectrum due to the evolution of Au nanoparticles at a temperature of 250 °C, which is further blue shifted at ∼554 nm with a narrower FWHM at 300 °C. The presence of Au nanoparticles is also confirmed by X-ray diffraction with Au (111) and Au (200) fcc reflections. Thermally induced transformations of fullerene C60 matrix at high temperatures is studied by Raman spectroscopy on pure fullerene C60 films (without metal). The blue shift of LSPR at a temperature of 300 °C is ascribed to the transformation of fullerene C60 matrix into amorphous carbon and is explained in terms of Mie theory. TEM results show the growth of Au nanoparticles in fullerene matrix at higher temperatures due to the enhanced diffusion of Au atoms and Ostwald ripening.

KARAKTERISASI IMPEDANSI LAPISAN TIPIS ZnS:Mn YANG DIBUAT DENGAN CO-EVAPORASI ZnS DAN Mn

The aim of this research is to characterize impedance, capasitance and relative permitivity of the characteristics of electric thin film ZnS and ZnS:Mn. This research was started from making thin film with different deposition speed and with thermal co-evaporation method in vakum tubes. The estimation is the characteristics of thin film ZnS impedance and ZnS:Mn was done outside this vacum with various frequency between thousaund to million hertzs, with different deposition speed and the same thickness. Defining impedance of ZnS thin film wich the most optimal frequency would influence capasitance and relative permittivity of the thin film on the characteristics of the electricity. Besides, capasitance and resitance values of ZnS:Mn thin film would change if given different Mn portion on that thin film. From the result of the research, it could be identified as follows. On the area of the thousand to ten thousand Hertz, it was know is that relative permitivity/constante static dielectrics K(0) ZnS:Mn thin film was not the frequency function that it could be regarded as constant like K(o) = 10. The price of capasitance ZnS:Mn was increasing with less Mn amount in that thin film. The price of ZnS:Mn electric resitance is reduced with less Mn amount on that thin film. Key words: Impedance, thin film ZnS:Mn, co-evaporation.

Growth and Characterizations of Tin-Doped on Nickel-Phthalocyanine as a Novel Nanomaterial

Tin-doped nickel phthalocyanine thin films (Sn-doped NiPc) were deposited by thermal co-evaporation method. Doping concentration of tin in NiPc was controlled via different deposition rates between metal dopent and host organic material. Properties of the thin films doped by tin in the range of 3 to 15% were characterized by atomic force microscopy (AFM), field emission scanning electron microscopy (FESEM), UV-Visible spectroscopy and X-ray photoelectron spectroscopy (XPS). Furthermore, electrical properties of Al/Sn-doped-NiPc/ITO devices i.e. charge carrier concentration and carrier mobility were characterized by current-voltage and capacitance-voltage measurements. Microscopic results show clear evidence of the morphological transition from granular structure in undoped-film to rod-liked structure in the films doped more than 5%. Moreover, surface grain size exhibits the tendency to decrease with the increase of doping concentration. Optical properties reveal that the packing of NiPc molecules in all doping conditions is the combination of α-phase (majority) and β-phase (minority). However, evolution of β-phase NiPc is observed with the increase of doping concentration. Photoelectron analyses indicate shift of binding energy in both Ni2p and Sn3d levels corresponding to charge transfer between nickel-core and tin dopant. In addition, the electrical properties show the enhancement of the film’s conductivity due to the increase of charge carrier concentration with the higher Sn-doping level.

Annealing effects on the thermoelectric properties of silver-doped bismuth telluride thin films

The structures and thermoelectric properties of n-type silver-doped Bi2Te3 thin films on SiO2/Si substrates using thermal co-evaporation method were reported. Annealing effects on the thermoelectric properties of thin films were also investigated in the temperature range 100 to 250°C under nitrogen atmosphere. The crystalline structures and morphologies were examined by X-ray diffraction and field emission scanning electron microscope. The thermoelectric properties of thin films were determined by Seebeck coefficients and electrical conductivity measurements. The results showed that as the thin film is annealed at 250°C, the Seebeck coefficient and electrical conductivity of −47.04μV/K and 976.13S·cm−1 can be obtained, respectively, which resulted in an optimum power factor of about 2.16μW/cm·K2.