G. K. Solanki

Growth and surface topography of WSe2 single crystal

Tungsten Di-Selenide belongs to the family of TMDCs showing their potential applications in the fields of Optoelectronics and PEC solar cells. Here in the present investigation single crystals of WSe2 were grown by Direct Vapour Transport Technique in a dual zone furnace having temperature difference of 50 K between the two zones. These single crystals were characterized by EDAX which confirms the stiochiometry of the grown crystals. Surface topography of the crystal was studied by optical micrograph showing the left handed spirals on the surface of WSe2 crystals. Single crystalline nature of the crystals was confirmed by SAED.

Growth and thermal properties of GeSePb0.4 single crystals

Single crystals of GeSePb0.4 were grown by Direct Vapor Transport (DVT) technique, in a two zone horizontal furnace with temperature difference of 50 K between growth and source zones. The material crystallizes in the form of shining gray and platelets like crystals at the end of growth cycles. Thermogravimetric analysis (TGA) has been used for many years to evaluate thermal stability of material as it will determine the range of stable operation for a device made up out of these materials under investigation. Thermal characteristics of GeSePb0.4 crystals were studied employing thermoanalytical techniques, viz. TGA and DTA. Thermal analysis experiments were carried out with constant heating rate of 10°C/ min in air. The DTA pattern of GeSePb0.4 crystals shows a strong endothermic peak at 472°C. The objective of this study is to determine activation energy and other kinetic parameters of GeSePb0.4 crystals. Broido and Coats-Redfern models are used to evaluate different kinetic parameters of GeSePb0.4 cryst...

Growth and photo-response of NbSe2 and NbS2 crystals

Transition metal dichalcogenides(TMDCs) have attracted intense research efforts due to their drastic properties change as we move towards ultra-thin crystalline layers from their bulk counterparts. Many well studied members of this family such as MoS2, WS2, WSe2, WS2 etc. have shown potential for flexible electronic devices including photovoltaic applications. The TMDCs like NbSe2 and NbS2 are relatively less studied layered compounds consisting of staked sandwiches of Se-Nb-Se/S-Nb-Se tri-layers with strong covalent/ionic intra layer bonds and weak Van der Waals interlayer interactions. In the present work, author have grown the crystals of NbSe2 and NbS2 by Direct Vapour Transport (DVT) technique and the material composition is confirmed using EDAX data. Photoelectrochemical (PEC) solar cell measurements are performed under monochromatic light illumination at different intensities and various solar cell parameters are calculated. These crystalline semiconductor electrodes were also analysed by photocurrent-voltage characteristics in a PEC solar cell structure (Cu/NbSe2/(0.1M K4Fe(CN)6 + 0.1M K3Fe(CN)6) and Cu/NbS2/(0.1M K4Fe(CN)6 +0.1M K3Fe(CN)6)). Blue coloured light gave the maximum efficiency. For further analysis of photodetection properties of the grown crystals, Ag painted broad low contact resistance electrical contacts were drawn from the crystals and its transient photoresponse was studied to evaluate different detector parameters.Transition metal dichalcogenides(TMDCs) have attracted intense research efforts due to their drastic properties change as we move towards ultra-thin crystalline layers from their bulk counterparts. Many well studied members of this family such as MoS2, WS2, WSe2, WS2 etc. have shown potential for flexible electronic devices including photovoltaic applications. The TMDCs like NbSe2 and NbS2 are relatively less studied layered compounds consisting of staked sandwiches of Se-Nb-Se/S-Nb-Se tri-layers with strong covalent/ionic intra layer bonds and weak Van der Waals interlayer interactions. In the present work, author have grown the crystals of NbSe2 and NbS2 by Direct Vapour Transport (DVT) technique and the material composition is confirmed using EDAX data. Photoelectrochemical (PEC) solar cell measurements are performed under monochromatic light illumination at different intensities and various solar cell parameters are calculated. These crystalline semiconductor electrodes were also analysed by photocurr...

Investigation of transient photoresponse of WSSe ternary alloy crystals

Transition metal chalcogenides have been studied intensively in recent time due to their tunability of electronic properties by compositional change, alloying and by transforming bulk material into crystalline 2D structure. These changes lead to the development of verities of next generation opto-electronic device applications such as solar cells, FETs and flexible detectors etc. In present work, we report growth and characterization of crystalline ternary alloy WSSe by direct vapour transport technique. A photodetector is constructed using grown crystals to study its transient photoresponse under polychromatic radiation. The WSSe crystals are mechanically exfoliated to thickness of 3 µm and the lateral dimension of prepared sample is 2.25 mm2. The time-resolved photoresponse is studied under polychromatic illumination of power density ranging from 10 to 40 mW/cm2. The photo response is also studied under different bias voltages ranging from 0.1 V to 0.5 V. The typical photodetector parameters i.e. photocurrent, rise and fall time, responsivity and sensitivity are evaluated and discussed in light of the ternary alloy composition.Transition metal chalcogenides have been studied intensively in recent time due to their tunability of electronic properties by compositional change, alloying and by transforming bulk material into crystalline 2D structure. These changes lead to the development of verities of next generation opto-electronic device applications such as solar cells, FETs and flexible detectors etc. In present work, we report growth and characterization of crystalline ternary alloy WSSe by direct vapour transport technique. A photodetector is constructed using grown crystals to study its transient photoresponse under polychromatic radiation. The WSSe crystals are mechanically exfoliated to thickness of 3 µm and the lateral dimension of prepared sample is 2.25 mm2. The time-resolved photoresponse is studied under polychromatic illumination of power density ranging from 10 to 40 mW/cm2. The photo response is also studied under different bias voltages ranging from 0.1 V to 0.5 V. The typical photodetector parameters i.e. photoc...

Effect of doping on all TMC vertical heterointerfaces

The present work reports the growth and basic characterizations of GeSePbx (x=0, 0.02, 0.04) layered mono chalcogenide single crystal substrates for preparation of heterojunction devices. These crystals are grown by Direct Vapour Transport (DVT) Technique [1,2]. Heterojunction interfaces on these substrates are prepared using thermal evaporation of nanocrystalline SnSe thin films having 5kA thickness. The electrical characterizations reveal the rectifying behavior of the devices based on which its ideality factor, barrier height, saturation current, series resistance etc. have been determined using thermionic emission model [3,4]. The device parameters have been determined and analyzed by three different methods viz. LnI-V, Cheung’s method and Norde method [5]. The variation in the device parameters in light of doping is reported in the present work.The present work reports the growth and basic characterizations of GeSePbx (x=0, 0.02, 0.04) layered mono chalcogenide single crystal substrates for preparation of heterojunction devices. These crystals are grown by Direct Vapour Transport (DVT) Technique [1,2]. Heterojunction interfaces on these substrates are prepared using thermal evaporation of nanocrystalline SnSe thin films having 5kA thickness. The electrical characterizations reveal the rectifying behavior of the devices based on which its ideality factor, barrier height, saturation current, series resistance etc. have been determined using thermionic emission model [3,4]. The device parameters have been determined and analyzed by three different methods viz. LnI-V, Cheung’s method and Norde method [5]. The variation in the device parameters in light of doping is reported in the present work.

Growth, morphological properties and pulsed photo response of MoTe2 single crystal synthesized by DVT technique

Molybednum Di Telluride of group VI belongs to the family of layered transition metal di-chalcogenides (TMDCs). These TMDCs show good potential for applications in the field of optoelectronic devices as they are chemically inert trilayered structure of MX2 type. In the present investigation crystals of MoTe2 are grown by direct vapor transport technique in a dual zone horizontal furnace. The grown crystals were characterized by Energy Dispersive Analysis of X-rays (EDAX) to study its elemental and stoichiometric composition, Selected Area Electron Diffraction (SAED) confirms the hexagonal structure. Spot pattern of electron diffraction shows formation of single phase. Scanning Electron Microscope (SEM) shows the layer by layer growth of the crystals, Thermo Electric Power (TEP) reflects the p-type semiconducting nature of the grown crystals. As this material is photosensitive material having band gap of approximately 1.0 eV, a transient photo response against polychromatic radiation (40 mW/cm2) of photodetector is also measured which showed slow decay in generated photocurrent due to low trapping density within the active area of the prepared device. Thus, it shows that this material can be a good photovoltaic material for constructing a solar cell also.Molybednum Di Telluride of group VI belongs to the family of layered transition metal di-chalcogenides (TMDCs). These TMDCs show good potential for applications in the field of optoelectronic devices as they are chemically inert trilayered structure of MX2 type. In the present investigation crystals of MoTe2 are grown by direct vapor transport technique in a dual zone horizontal furnace. The grown crystals were characterized by Energy Dispersive Analysis of X-rays (EDAX) to study its elemental and stoichiometric composition, Selected Area Electron Diffraction (SAED) confirms the hexagonal structure. Spot pattern of electron diffraction shows formation of single phase. Scanning Electron Microscope (SEM) shows the layer by layer growth of the crystals, Thermo Electric Power (TEP) reflects the p-type semiconducting nature of the grown crystals. As this material is photosensitive material having band gap of approximately 1.0 eV, a transient photo response against polychromatic radiation (40 mW/cm2) of photode...

Photosensitive space charge limited current in screen printed CdTe thin films

Group II-VI Compounds have emerged out as most suitable in the class of photo sensitive material. They represent a strong position in terms of their applications in the field of detectors as well as photo voltaic devices. Cadmium telluride is the prime member of this Group, because of high acceptance of this material as active component in opto-electronic devices. In this paper we report preparation and characterization of CdTe thin films by using a most economical screen printing technique in association with sintering at 510°C temperature. Surface morphology and smoothness are prime parameters of any deposited to be used as an active region of devices. Thus, we studied of the screen printed thin film by means of atomic force microscopy (AFM) and scanning electron microscopy (SEM) for this purpose. However, growth processes induced intrinsic defects in fabricated films work as charge traps and affect the conduction process significantly. So the conduction mechanism of deposited CdTe thin film is studied under dark as well as illuminated conditions. It is found that the deposited films showed the space charge limited conduction (SCLC) mechanism and hence various parameters of space charge limited conduction (SCLC) of CdTe film were evaluated and discussed and the photo responsive resistance is also presented in this paper.Group II-VI Compounds have emerged out as most suitable in the class of photo sensitive material. They represent a strong position in terms of their applications in the field of detectors as well as photo voltaic devices. Cadmium telluride is the prime member of this Group, because of high acceptance of this material as active component in opto-electronic devices. In this paper we report preparation and characterization of CdTe thin films by using a most economical screen printing technique in association with sintering at 510°C temperature. Surface morphology and smoothness are prime parameters of any deposited to be used as an active region of devices. Thus, we studied of the screen printed thin film by means of atomic force microscopy (AFM) and scanning electron microscopy (SEM) for this purpose. However, growth processes induced intrinsic defects in fabricated films work as charge traps and affect the conduction process significantly. So the conduction mechanism of deposited CdTe thin film is studied ...

The study of photoelectrochemical behavior of germanium sulphoselenide crystals on enhancement of sulpher content

This paper represents the investigation on growth of single crystals of Germanium Sulpho Selenide using Direct Vapour Transport Technique. The stoichiometries of the grown crystals have been analyzed using EDAX which shows that the grown crystals possess nearly stoichiometric proportion of starting material. The orthorhombic semiconducting compound GeS0.25Se0.75, GeS0.5Se0.5 and GeS0.75Se0.25 having various interesting electrical, optical and photoelectric properties. Using UV-VIS-NIR spectrophotometer optical absorption spectra of the crystals to obtain direct and indirect band gap of the material. Author has attempted to fabricate Photo Electro Chemical solar cell with grown mixed Germanium Sulphoselenide single crystals. MottSchottky plots have been used to study the energy band location and redox analysis of the material. This study justifies the appropriate choice of electrolyte for PEC work. The solar cell parameters e.g. the fill factor (FF), open circuit voltage (Voc), short circuit current (Isc) and efficiency (η) for all the cells have been calculated. All the results have been studied and implications have been discussed in the paper.

Preparation of H2SO4 doped Polyaniline thin film solar cells by spin coating technique

A water diluted H2SO4 solution was used to dissolve Polyaniline in order to obtain a solution for preparation of thin films by spin coating technique. The chemical bonding characteristics of the prepared films were investigated using Furrier transform infrared spectroscopy (FTIR) and the structural characterizations were accomplished by X-ray diffraction (XRD). UV-VIS absorption spectroscopy was used to determine the optical band gap of the deposited PANi films and the indirect optical band gap of PANi was estimated to be in the range of 1.3 to 1.8 eV from the Tauc’s plot. Further, these films were deposited on the n-MoSe2 crystal in order to complete a solar cell structure. The polychromatic photo response of the prepared solar cells for different intensities was studied at room temperature and the efficiency and fill factor were found to be 1% and 0.26 respectively. The obtained Photo-conversion characteristics (I-V) were also used to determined series and shunt resistances of the prepared device. The s...

Structural and Electrical Properties of ZnTe Thin Films Deposited at Various Substrate Temperatures

The structural and electrical properties of ZnTe thin films were investigated as a function of substrate temperature. Vacuum evaporated thin films of Zinc Telluride (ZnTe) of 10kÅ thickness have been deposited on ultrasonically cleaned glass substrates at various substrate temperatures (303K, 373K 448K). Structural parameters were obtained using XRD analysis. It was observed that the films deposited were cubic in nature with a strong (111) texture. Electrical parameters (Hall Effect measurement) have been obtained and studied at various temperatures in the range 303-393K. It is observed that Hall coefficient remains positive throughout the whole temperature range indicating that holes are the majority carriers. The results obtained from structural and electrical parameters study have been correlated and it is found that the thin films deposited at higher substrate temperatures possess increasingly good crystalline structure with improved electrical conductivity along with an increase in carrier concentration and mobility of carriers.