Increase In Carrier Concentration Research Articles

Optical and Thermoelectric Properties of Surface-Oxidation Sensitive Layered Zirconium Dichalcogenides ZrS2−xSex (x = 0, 1, 2) Crystals Grown by Chemical Vapor Transport

In this work, structure, optical, and thermoelectric properties of layered ZrS2−xSex single crystals with selenium composition of x = 0, 1, and 2 were examined. Single crystals of zirconium dichalcogenides layer compounds were grown by chemical vapor transport method using I2 as the transport agent. X-ray diffraction (XRD) and high-resolution transmission electron microscope (HRTEM) results indicated that ZrS2−xSex (x = 0, 1, and 2) were crystalized in hexagonal CdI2 structure with one-layer trigonal (1T) stacking type. X-ray photoelectron and energy dispersive X-ray measurements revealed oxidation sensitive behavior of the chalcogenides series. Transmittance and optical absorption showed an indirect optical gap of about 1.78 eV, 1.32 eV, and 1.12 eV for the ZrS2−xSex with x = 0, 1, and 2, respectively. From the result of thermoelectric experiment, ZrSe2 owns the highest figure-of merit (ZT) of ~0.085 among the surface-oxidized ZrS2−xSex series layer crystals at 300 K. The ZT values of the ZrS2−xSex (x = 0, 1, and 2) series also reveal increase with the increase of Se content owing to the increase of carrier concentration and mobility in the highly Se-incorporated zirconium dichalcogenides with surface states.

Oxygen vacancies engineering in TiO2 homojunction/ZnFe-LDH for enhanced photoelectrochemical water oxidation

The high-efficiency separation and transfer of photogenerated electrons and holes are significant to achieve highly photoelectrochemical water redox efficiency. Here, we integrate anatase TiO2 with moderate oxygen vacancies and ZnFe-LDH cocatalyst on 3D homojunction r-TiO2(rutile TiO2)/a-TiO2(anatase TiO2) photoanode to promote the separation and transfer efficiency of carriers for a high photoelectrochemical activity. The as-prepared r-TiO2/a-TiO2/ZnFe-LDH photoanode demonstrates an enhanced photocurrent density of 1.86 mA cm−2 at 1.23 V vs. RHE and the onset potential of 0.26 V vs. RHE, 2.55 times and 100 mV cathodic shift by contrast with those of bare r-TiO2. The experimental and calculated results suggest the improved electron transport by oxygen vacancies and r-TiO2/a-TiO2 with matched energy bands, along with the accelerated hole capture and facilitated surface oxygen production reaction kinetics by cocatalyst ZnFe-LDH. The compare researches for the sample without the oxygen vacancies are introduced to further illustrate the increased carrier concentration and conductivity caused by oxygen vacancies. This work manifests the effective use of oxygen vacancies in regulating carriers transport and provides a novel strategy for manufacturing high-performance photoanodes in photoelectrochemical water splitting.

Electronic and ionic conduction in ligand-free lead selenide colloidal quantum dots

We fabricated a ligand-free lead selenide (PbSe) colloidal quantum dot (CQD) film and probed its electrical properties using a field-effect transistor (FET) at low temperature. The contribution of the ionic conduction to the electrical properties in the PbSe CQD film became significant after ligand removal using ammonium sulfide [(NH4)2S], evidenced by temperature-dependent FET mobility, threshold voltage, and current hysteresis depending on gate scan direction. The enhanced FET mobility and increased carrier concentration at a lower temperature are attributed to reduced ionic conduction, suppressing the gate electric field screening at the PbSe/SiO2 interface.

The Impact of Maltodextrin and Inulin on the Protection of Natural Antioxidants in Powders Made of Saskatoon Berry Fruit, Juice, and Pomace as Functional Food Ingredients.

The objective of this study was to examine the effect of inulin and maltodextrin applied during vacuum drying of Saskatoon berry fruit, juice, and pomace on the retention of bioactive compounds and antioxidant capacity (radical scavenging capacity (ABTS), ferric reducing antioxidant potential (FRAP)) of powders obtained. Ultra-high performance liquid chromatography (UPLC-PDA-ESI-MS/MS) was used to identify major groups of polyphenolic compounds, such as: flavan-3-ols (35% of all polyphenols for fruit powder, 33% for juice powder, and 39% for pomace powders of all polyphenols), anthocyanins (26% for fruit powder, 5% for juice powder, and 34% for pomace), phenolic acids (33% for fruit powder, 55% for juice powder, and 20% for pomace powder), and flavanols (6% for fruit powder, 6% for juice powder, and 7% for pomace powder). In general, the content of polyphenols was more dependent on the content than on the type of carrier used for drying, regardless of the matrix tested. The average sum of polyphenols and the antioxidant activity (for ABTS and FRAP assay) of the powders with 30% of carrier addition were 5054.2 mg/100 g dry matter (d.m.) as well as 5.3 and 3.6 mmol Trolox/100 g d.m. in the ABTS and FRAP tests, respectively. The increase in carrier concentration by 20% caused a decrease of 1.5-fold in the content of polyphenols and a 1.6-fold and 1.5-fold in the antioxidant potential, regardless of the matrix tested. The principal component analysis (PCA) analysis indicated that the freeze-drying process led to the lowest degradation of the identified compounds, regardless of the matrix tested, with the exception of juice and pomace powders dried by vacuum drying at 60 °C. In this case, the release of (−)-epicatechin was observed, causing an increase in the flavanol contents. Thus, this work demonstrated the effect of processing and matrix composition on the preservation of antioxidant bioactives in Saskatoon berry powders. Properly designed high-quality Saskatoon berry powders with the mentioned carriers may be used as nutraceutical additives to fortify food products and to improve their functional properties.

Manipulating the intrinsic vacancies for enhanced thermoelectric performance in Eu2ZnSb2 Zintl phase

Zintl compounds have caught great attention in thermoelectric applications due to their intrinsic “electron-crystal, phonon-glass” structures. Previous studies suggested that Zintl-phase Eu 2 ZnSb 2 was a promising thermoelectric material due to its ultralow thermal conductivity. In this work, we used Ag to regulate the Zn–Sb framework for enhanced electrical properties, and prepared Eu 2 Zn 1-0.5 x Ag x Sb 2 ( x = 0.02, 0.06, and 0.1) by ball milling and spark plasma sintering. The additional Ag fills the initial vacancies and causes both increased carrier concentration and mobility. The maximum ZT reaches ~0.92 at 823 K for Eu 2 Zn 0.97 Ag 0.06 Sb 2 . By further reducing the Zn content, the carrier concentration increases close to the optimum value, and a peak ZT value of ~1.1 at 823 K was achieved for Eu 2 Zn 0.95 Ag 0.06 Sb 2 . • Ag was used to regulate the Zn–Sb framework of Eu 2 ZnSb 2 for enhanced electrical properties. • The additional Ag fills the initial vacancy and causes both increased carrier concentration and mobility. • The carrier concentration increases close to the optimum value by further reducing the Zn content. • A peak ZT value of ~1.1 at 823 K was achieved for Eu 2 Zn 0.95 Ag 0.06 Sb 2 .

Hydrogen plasma-treated 1D/3D TiO2 nanorod array photoanode for efficient photoelectrochemical water splitting

The rutile phase titanium oxide (TiO2) based photoanode exhibits less energy conversion efficiency, as compared to anatase phase TiO2 photoanode. Enhancing the performance of the rutile phase TiO2 photoanode in a photoelectrochemical cell for water splitting is a significant challenge. In this study, we have grown the rutile phase 1D/3D nanorod array structure by using a one-step hydrothermal process. To enhance the surface properties of 1D/3D TiO2 nanorod array films, the as-grown films were treated in a hydrogen plasma atmosphere created using an electron cyclotron resonance (ECR) plasma system. The crystalline phases of the untreated and Hydrogen plasma treated films are confirmed by XRD and Raman studies. We found that, hydrogen plasma treatment creates Ti3+ sites and oxygen vacancies, leading to an increment in optical absorbance and reducing the band gap from 3.17 to 2.89 eV. Additionally, a significant enhancement in photocurrent density (0.369 mAcm−2 at 1 V versus Ag/AgCl) was observed in hydrogen plasma-treated 1D/3D TiO2 nanorod array photoanodes compared to untreated films (0.034 mAcm−2 at 1 V). The enhancement is attributed to the increase in carrier concentration induced by oxygen vacancy formation and the improved electron-hole pair separation. Further, the hydrogen plasma-treated 1D/3D TiO2 nanorod array photoanode exhibited high Photostability for long time duration.

Feasibility of Polysulfone as Base Polymer in a Polymer Inclusion Membrane: Synthesis and Characterisation

Polysulfone was investigated as an alternative base-polymer for polymer inclusion membranes (PIM’s) that could withstand harsh environmental conditions and have good transport efficiency of metal ions. PIM’s were prepared using polysulfone as a base polymer and Aliquat 336 as a carrier in the absence of a plasticizer. Chromium (VI) was used as standard to study the extraction efficiency of the membranes. The optimal composition ratio for the membrane with the highest extraction efficiency during passive sampling of the chromium (VI) from solution was 40:60 (w/w) polysulfone: Aliquat 336. This membrane had a flux of 8.68×10-7 mol.m-2.s-1 and had increased chemical stability over a range of pH 2 – 12 compared to poly(vinyl chloride) based membranes. The presence of functional groups on the polysulfone, Aliquat 336 and the synthesized polymer inclusion membrane were confirmed using Fourier Transformed Infrared Spectroscopy. The results showed that only physical interaction exists between the carrier and the polymer matrix. Scanning electron microscopy and atomic force microscopy indicated that the membrane surface was dense and the roughness increased with an increase in carrier concentration. The hydrophilicity of the membranes was studied using a drop shape analyser. The results revealed that an increase in carrier concentration increases the membrane’s hydrophilicity. Thermal stability was investigated and the membranes were found to be stable up to 180 ⁰C.

Carrier concentration increase in OFETs with interface barrier and Fermi level difference

It was found that interface barrier is beneficial to form accumulation heterojunction in organic semiconductor. A new theoretical model has been established with combined effect of interface barrier and EF level difference between p-type and n-type materials. The organic pn-heterojunction has been put forward in OFETs for further research, 2 nm perylene diimide (PDI) and its derivatives (PDI-1)/(PDI-2) are used as discontinuous films to modify pentacene OFETs. The accumulative effect will be further enhanced under the joint effect of interface barrier and greater EF level difference. With the downgrading of LUMO level for n-type materials, the hole concentration in pentacene was increased by 12.3 times, 36.9 times and 107.4 times respectively, and VT shifted from −6.90 V to −2.67 V, 0.64 V and 6.82 V, the OFETs performance have been optimized efficiently, and the devices can be converted from enhancement-mode to depletion-mode. The LUMO level of PDI-2 was pinned to the EF level of pentacene has been verified by employing the organic-organic interface energy level alignment (OOI ELA) theory. The dramatic increase of carrier concentration is theoretically revealed at both sides of pn-heterojunction.

Realizing a High ZT of 1.6 in N-Type Mg3Sb2-Based Zintl Compounds through Mn and Se Codoping.

Mg3Sb2-based compounds by virtue of nontoxicity and low-cost have become a promising class of candidates for midtemperature thermoelectric power generation. Here, we successfully fabricated n-type Mg3Sb2-based materials using an inexpensive and efficient approach of one-step ball milling and spark plasma sintering, and demonstrate that a complementary and favorable effect of multiple elements coalloying/-doping leads to an excellent thermoelectric performance. The intrinsic p-type conducting behavior for Mg3Sb2 could be changed to n-type through Bi and Se coalloying on Sb sublattices with excess Mg, resulting from the suppression of Mg vacancies and the formation of Mg interstitial. Furthermore, Mn doping on Mg sublattices could soften the chemical bonds, leading to the increase of carrier mobility and concentration simultaneously. Additionally, multielement coalloying/-doping could significantly increase the lattice disorder, which undoubtedly strengthens the phonon scattering and readily results in a suppressed lattice thermal conductivity. As a result, a highest ZT value of 1.6 at 723 K and an average ZT value up to 1.1 were obtained in the temperature range of 323-723 K in the Mg3.18Mn0.02Sb1.5Bi0.49Se0.01 sample, which is one of the highest values among the Te free Mg3Sb2. This work could give guidance for improving the thermoelectric performance of Zintl phase materials or even others using the multielement codoping/-alloying strategy.

Mechanism of Cs0.33TaxW1-xO3 in improving the optical property

In this study, Ta5+ doped Cs0.33WO3 with the excellent near-infrared shielding and transparent thermal performance is successfully prepared via a simple one-pot hydrothermal route. The synthetic procedure and optical response of the obtained samples are systematically investigated by various analytical instruments and the mechanism of doping Ta5+ into Cs0.33WO3 is studied in this work. The results indicate a significant improvement in the optical property after the doping. The carrier concentration and free-electrons increase because of the lattice distortion. Further more when the ratio x of Ta/(Ta + W) = 0.05, the as-prepared Cs0.33Ta0.05W0.95O3 exhibits improved visible light transparency of 85.91% and the near-infrared shielding ability of 80.60%. This improvement could be attributed to the maximum carrier concentration and free electrons in Cs0.33Ta0.05W0.95O3.

Equal channel angular extrusion: An effective method to refine the microstructure of cast n-type Bi2Te3 based ingot to co-optimize thermoelectric and mechanical properties

Although the mechanical strength of n-type polycrystalline Bi2Te3 based alloys prepared by conventional powder metallurgy technology is good, its thermoelectric properties have poor repeatability and contamination is introduced. In this work, n-type polycrystalline Bi2Te3 based alloys with uniform microstructure were fabricated by applying equal channel angular extrusion (ECAE) method to extrude the cast ingot directly for four passes at 783 K. The initial lamellae coarse grains with hundreds of microns were broken down efficiently and refined uniformly to only 10–20 μm. And the Vickers hardness was increased by 2.3 times due to the refined grains. On the other hand, it is noteworthy that the ECAE process is also an ideal method to improve the thermoelectric properties of cast ingot by boosting electrical transport properties due to the donor like effect induced by heavy deformation and reducing thermal transport properties due to the enhanced phonon scattering. In order to further optimize the thermoelectric performance, BiCl3 doping was used to precisely tune the carrier concentration to the best range. The intrinsic excitation temperature of Bi2Te3 based alloys gradually shifted from low temperature (below 303 K) to high temperature (463 K) owing to the increased carrier concentration. Finally, the extruded Bi2Te3 based alloy doped with 0.064 wt % BiCl3 obtained the maximum dimensionless figure of merit (ZT) of 0.68 at 423 K, which was far higher than the nearly zero of the initial cast ingot.

Development and Characterization of Solid Dispersion System for Enhancing the Solubility and Dissolution Rate of Dietary Capsaicin

Background:Capsaicin is a pungent component of chili peppers that suppresses the growth of various cancer cell lines including breast cancer. However, it shows extremely low oral bioavailability due to its poor water solubility.Objective:The objective of the present work was to improve the solubility and dissolution rate of capsaicin.Methods:Solid dispersions were prepared by the solvent evaporation method using different molar ratios of capsaicin and urea (1:1, 1:2, and 1:3). Differential Scanning Calorimetry (DSC) and X-Ray Diffraction (XRD) study were used to characterize the solid dispersion. Solid dispersions were evaluated for solubility, dissolution rate and in vitro cytotoxicity in breast cancer cell lines.Results:XRD and DSC studies exhibited the reduced crystallinity of a drug in solid dispersion. Phase solubility study shows that the drug solubility increased by increasing carrier concentration. In vitro release study of the solid dispersion showed the faster dissolution of a drug with increasing carrier concentration. Solid dispersion formulation effectively inhibited the growth of MCF-7 human breast cancer and MDA-MB-231 triple negative human breast cancer cells in an MTT assay that measures metabolic activity, but only slightly decreased cell viability when compared to capsaicin alone.Conclusion:The present study demonstrated that solid dispersion of capsaicin in PEG 6000 overcomes the problems related to the poor aqueous solubility of this drug and improving its dissolution rate.

Sample Preparation of TiO<sub>2</sub> Added ZnO Using Powder Metallurgy Route and its Characteristics

Metal oxide semiconductor gas sensors have been widely utilized in a variety of different roles and industries. They are relatively inexpensive, robust, lightweight, long lasting and benefit from high material and quick response time compared to other sensing technologies. However, there are major challenges need to overcame by developers in order to construct a semiconductor metal oxide gas sensor that is efficient, and durable and most importantly can work at lower temperature. Therefore, in this research, TiO2 dopants was introduced into conventional high purity ZnO gas sensor whereby the samples were prepared in pellet form using powder metallurgy route. The improvement in the mechanical properties as well as the electrical properties of the samples was wished to be observed through this research. The density measurement showed that the adding of TiO2 was efficient to promote the densification of ZnO sample in which 9 wt% TiO2 doped ZnO sample showed the highest density. The XRD results showed that the diffraction pattern was basically attributed to the wurtzite structure of ZnO. This was proven by the plane (1 0 1) had the highest intensity in all the samples except 6 wt% TiO2 and 9 wt% TiO2 doped ZnO sample. SEM showed that the grain size of ZnO decreased with the addition of TiO2. This was caused by the formation of the new phase which was Zn2TiO4. The smaller the grain size, the higher the specific surface area and oxygen adsorption quantity, and therefore the higher the gas sensitivity is. UV-Vis showed that the wavelength of all samples was located around 380 nm. Therefore, the calculated exitonic energy was around 3.20 eV which was nearly matched with the theoretical band gap of ZnO (3.37 eV). The measurement of the resistivity using four point probe showed that the electrical resistivity of the samples decrease up to addition of 9 wt% TiO2. This was attributed to increased carrier concentration. Vickers hardness test showed that the doping of TiO2 had increased the hardness of the sample whereby the 9 wt% TiO2 doped ZnO sample showed the highest value of hardness. The addition of TiO2 into high purity ZnO has influenced the mechanical and electrical properties of ZnO. From observing the microstructural and density measurement to the measurement of the surface resistivity as well as the determination of the Vickers hardness value, it was found that 9 wt% TiO2 doped ZnO was predicted as a candidate for substituting a conventional high purity ZnO as the gas sensor.

Ultra-high open-circuit voltage of tin perovskite solar cells via an electron transporting layer design

Tin perovskite is rising as a promising candidate to address the toxicity and theoretical efficiency limitation of lead perovskite. However, the voltage and efficiency of tin perovskite solar cells are much lower than lead counterparts. Herein, indene-C60 bisadduct with higher energy level is utilized as an electron transporting material for tin perovskite solar cells. It suppresses carrier concentration increase caused by remote doping, which significantly reduces interface carriers recombination. Moreover, indene-C60 bisadduct increases the maximum attainable photovoltage of the device. As a result, the use of indene-C60 bisadduct brings unprecedentedly high voltage of 0.94 V, which is over 50% higher than that of 0.6 V for device based on [6,6]-phenyl-C61-butyric acid methyl ester. The device shows a record power conversion efficiency of 12.4% reproduced in an accredited independent photovoltaic testing lab.

Simultaneously increased carrier concentration and mobility in p-type Bi0.5Sb1.5Te3 throng Cd doping

To improve the thermoelectric properties of a material, the carrier concentration needs to be optimized first. But the increase of carrier concentration usually results in degraded carrier mobility, which restricts the enhancement in thermoelectric performance. Herein, we report the Cd doped Bi0.5Sb1.5Te3 which overcomes such a trade-off between carrier concentration and mobility. The doping of Cd results in significantly increased hole concentration, which successfully suppresses the bipolar diffusion. Meanwhile, magnetic measurements indicate that the Hall mobility increases with the doping of Cd owing to the decrease of anti-site defects. Thus, simultaneous increase of carrier concentration and mobility is realized in p-type Bi0.5Sb1.5Te3 through Cd doping, resulting in significantly enhanced power factor. In addition, the lattice disorder induced by the substitution of Cd for Sb/Bi leads to an obvious reduction in lattice thermal conductivity. As a result, a zT value of 1.2 at 120 °C is achieved for the 2 at% Cd doped sample. The peak zT of the 4 at% Cd doped sample is shifted to 185 °C due to the effectively suppressed bipolar effect and an average zT value of ∼1.0 is obtained in the temperature range of 50–300 °C. Our achievement demonstrates that there is still a significant room to improve the thermoelectric properties of the intensively investigated BiSbTe system by simply doping a properly selected element.

Structural, surface morphological, optical and thermoelectric properties of sol–gel spin coated Zn doped CdS thin films

The present work is focussed on Zinc (2, 4, 6, 8 and 10 wt%) doped CdS thin films synthesized by sol–gel spin coating method and deposited on glass substrates. X-ray diffraction patterns of Zn doped CdS thin films exhibit cubic structure. The microstructural properties such as crystallite size, lattice constant, microstrain, dislocation density and stacking fault probability in the films were reported. The surface morphology and topography of the films was studied by using field emission scanning electron microscopy and atomic force microscopy. The incorporation of Zn in CdS and elemental composition of the films has been confirmed with X-ray photoelectron spectroscopy (XPS) and energy dispersive spectroscopy (EDS). Raman spectrum of Zn doped CdS thin films exhibits 1LO and 2LO phonon modes. The optical band gap of CdS thin films increased from 2.63 to 2.73 eV with the increase of Zn dopant from 2 to 10%. Thermoelectric power measurements show negative Seebeck coefficient indicating n-type semiconducting behaviour. The carrier concentration of Zn doped CdS thin films at room temperature are found to be in the range of 1019–1020 cm−3 suggesting that the prepared films are degenerate semiconductors. The increase in thermal conductivity of Zn doped CdS thin film is due to the increase in carrier concentration of the films. The lattice thermal conductivity of Zn doped CdS thin films had an inverse temperature dependent and at high temperatures shows the dominance of phonon scattering.

Explicit Gain Equations for Single Crystalline Photoconductors.

Photoconductors based on semiconducting thin films, nanowires, and two-dimensional atomic layers have been extensively investigated in the past decades. However, there is no explicit photogain equation that allows for fitting and designing photoresponses of these devices. In this work, we managed to derive explicit photogain equations for silicon nanowire photoconductors based on experimental observations. The silicon nanowires were fabricated by patterning the device layer of silicon-on-insulator wafers by standard lithography that were doped with boron at a concentration of ∼8.6 × 1017 cm-3. It was found that the as-fabricated silicon nanowires have a surface depletion region ∼32 nm wide. This depletion region protects charge carriers in the channel from surface scatterings, resulting in the independence of charge carrier mobilities on nanowire size. Under light illumination, the depletion region logarithmically narrows down, and the nanowire channel widens accordingly. Photo Hall effect measurements show that the nanowire photoconductance is not contributed by the increase of carrier concentrations but by the widening of the nanowire channel. As a result, a nanowire photoconductor can be modeled as a resistor in connection with floating Schottky junctions near the nanowire surfaces. Based on the photoresponses of a Schottky junction, we derived explicit photogain equations for nanowire photoconductors that are a function of light intensity and device physical parameters. The gain equations fit well with the experimental data, from which we extracted the minority carrier lifetimes as tens of nanoseconds, consistent with the minority carrier lifetime in nanowires reported in literature.

Structural phase transition and manifestation of eddy currents in IR reflection spectra of PbSnTe semiconductor films

Infrared reflection spectra of thin (∼60 nm) Pb1−x SnxTe (x = 0.25, 0.53, 0.59) films grown by molecular beam epitaxy on GaAs/CdTe hybrid substrates have been measured at frequencies from 20 to 5500 cm−1 and temperatures from 5 to 300 K. The spectra have been used to determine temperature-dependent transverse phonon and plasmon frequencies in the films, which has made it possible to identify a structural phase transition at TC ≈ 50 K. The plasma frequency of the films has been shown to increase with decreasing band gap on cooling from 300 to 77 K. The increase in plasma frequency is mainly attributable to the increase in carrier concentration and a transition of the carriers from vortex states on the film surface to the valence band.

PHYSICAL PROPERTIES OF SUBLIMATED TERNARY COMPOUND CdZnS THIN FILMS

Mechanically mixed Cadmium Sulphide (CdS) powder with Zinc (Zn) (99.9% purity) was used as a source material to sublimate a ternary compound of Cadmium Zinc Sulphide (CdZnS) by using Closed Space Sublimation (CSS) under high vacuum. Annealing was carried out under optimized temperature and time for better diffusion of Zn into CdS. Xray diffraction (XRD) studies revealed that (002) was preferred orientation with hexagonal phase after annealing. Crystallite size of prepared films increased from 17 to 89 nm after annealing at higher temperatures. The surface morphology of the films was changed and the average composition of elements was confirmed by energy dispersive X-rays (EDX). The optical band gap energy increased from 2.42 eV and 2.45 eV after annealing. Electrically, the variation in mobility and increase in carrier concentration was due to the decrease of the grain boundary region. There was also variation in activation energy which confirmed the improvement in structure.

PHYSICAL PROPERTIES OF SUBLIMATED TERNARY COMPOUND CdZnS THIN FILMS

Mechanically mixed Cadmium Sulphide (CdS) powder with Zinc (Zn) (99.9% purity) was used as a source material to sublimate a ternary compound of Cadmium Zinc Sulphide (CdZnS) by using Closed Space Sublimation (CSS) under high vacuum. Annealing was carried out under optimized temperature and time for better diffusion of Zn into CdS. Xray diffraction (XRD) studies revealed that (002) was preferred orientation with hexagonal phase after annealing. Crystallite size of prepared films increased from 17 to 89 nm after annealing at higher temperatures. The surface morphology of the films was changed and the average composition of elements was confirmed by energy dispersive X-rays (EDX). The optical band gap energy increased from 2.42 eV and 2.45 eV after annealing. Electrically, the variation in mobility and increase in carrier concentration was due to the decrease of the grain boundary region. There was also variation in activation energy which confirmed the improvement in structure.