Hot Probe Research Articles

Effect of copper concentration on the physical properties of copper doped NiO thin films deposited by spray pyrolysis

The spray pyrolysis (SP) technique is an important and powerful method for the preparation of nickel oxide (NiO) and copper-doped nickel oxide thin films. The best films were obtained when the substrate temperature, Ts = 450 °C on glass substrates. Copper (Cu) concentrations in the films were varied from 0 to 8%. The effect of Cu concentration on the structural, morphological, spectral, optical, and electrical properties of the thin films were studied by X-ray diffraction (XRD), Scanning electron microscopy (SEM), Fourier transformed infrared spectroscopy (FTIR), UV–vis–NIR spectrophotometer, Hot probe and Hall system. The X-ray diffraction result shows the polycrystalline cubic structure of sprayed films with (200) preferred orientation. The variations of the structural parameters such as lattice parameters and grain sizes were investigated. The SEM image displays the surface morphology of the NiO and Cu:NiO thin films. The FTIR of the as-deposited films were associated with chemical identification. The optical transmittance and absorbance spectra of the films were measured by UV–vis–NIR spectrophotometer. The absorption coefficient and band gaps of the films were calculated using the optical method. All the NiO and Cu:NiO films were p-type. The resistivity of the above films decreases with the increase in copper concentration and so the conductivity of the films depend on the precursor concentration.

Measurement of Thermal Conductivities of Two Cryoprotective Agent Solutions for Vitreous Cryopreservation of Organs at the Temperature Range of 77 K-300 K Using a Thermal Sensor Made of Microscale Enamel Copper Wire.

Biobanking of organs by cryopreservation is an enabling technology for organ transplantation. Compared with the conventional slow freezing method, vitreous cryopreservation has been regarded to be a more promising approach for long-term storage of organs. The major challenges to vitrification are devitrification and recrystallization during the warming process, and high concentrations of cryoprotective agents (CPAs) induced metabolic and osmotic injuries. For a theoretical model based optimization of vitrification, thermal properties of CPA solutions are indispensable. In this study, the thermal conductivities of M22 and vitrification solution containing ethylene glycol and dimethyl sulfoxide (two commonly used vitrification solutions) were measured using a self-made microscaled hot probe with enameled copper wire at the temperature range of 77 K-300 K. The data obtained by this study will further enrich knowledge of the thermal properties for CPA solutions at low temperatures, as is of primary importance for optimization of vitrification.

Identification of Optical Transitions by Spectroscopic Ellipsometry (SE) on CuIn<sub>3</sub>Se<sub>5</sub> Bulk Compounds

Bulk materials were synthesized by the Bridgman technique using the elements Cu, In and Se. These samples were characterized by Energy Dispersive Spectrometry (EDS) to determine the elemental composition, as well as by X-ray diffraction for structure, hot point probe method for type of conductivity, Optical response (Photoconductivity) and Photoluminescence (PL) to determine the band gap value and Spectroscopic Ellipsometry to find energy levels above the gap in the band scheme at room-temperature. They show a nearly perfect stoechiometry and present a p-type conductivity. CuIn3Se5 either has a Stannite structure, an Ordered Defect Chalcopyrite structure (ODC), or an Ordered Vacancy Chalcopyrite structure (OVC). The gap energy obtained for the different samples was 1.23 eV. Energy levels above the gap in the band scheme were determinate by measuring the dielectric function at room temperature for energies lying between 1.5 and 5.5 eV. Many transitions were observed above the gap for different samples. Spectroscopic Ellipsometry gave evidence for the interpretation of the choice of gap values which were compatible with that obtained from solar spectrum.

Spectroscopic Ellipsometry Study of the Dielectric Function of Cu(In<sub>1–x</sub>Ga<sub>x</sub>)<sub>3</sub>Se<sub>5</sub> Bulk Compounds: Identification of Optical Transitions

Using Spectroscopic Ellipsometry (SE), the optical properties of Cu(In1−xGax)3Se5 bulk compounds, grown by the Bridgman method, were analyzed by varying x composition (0 ≤ x ≤ 1). Energy levels above the gap in the band scheme were determined by measuring the complex dielectric function at room-temperature for energies between 1.5 and 5.5 eV using a variable angle of incidence ellipsometer. The transitions values E1, E2 and E3 were observed above the gap for different samples of Cu(In1−xGax)3Se5 alloy. When a gallium atom replaces an indium atom, one assumes globally that the levels related to selenium and copper are unchanged. Conversely, the levels corresponding to the conduction band are shifted towards higher energies. Thus, the gap increases as the composition of gallium increases. Spectroscopic Ellipsometry (SE) gave evidence for the interpretation of the choice of gap values which were compatible with that obtained from solar spectrum. Several other characterization methods like Energy Dispersive Spectrometry (EDS), hot point probe method, X-ray diffraction, Photoluminescence (PL), Optical response (Photoconductivity) were presented in this paper. The Cu(In1−xGax)3Se5 have an Ordered Vacancy Chalcopyrite-type structure with lattice constants varying as a function of the x composition. The band gap energy of Cu(In1−xGax)3Se5 compounds is found to vary from 1.23 eV to 1.85 eV as a function of x.

Structural properties of sprayed CuInSSe thin films grown using different S/Se ionic ratios

We have grown nanocrystalline CuInSSe thin films on glass substrates using the spray pyrolysis technique at different S/Se ionic ratios 0.4 and 0.6. The CuInSSe films were co-deposited from aqueous solutions containing CuCl2, InCl3, thiourea and SeO2. The pH of the precursor solutions was kept at 10. Ethanolamine was used as an additive and the CuInSSe films were deposited at the constant temperature 300°C. The films were characterized by X-ray diffraction (XRD), and the results indicate that the films are single phase, polycrystalline having the chalcopyrite structure. The hot probe method indicates that the films are p-type in conductivity. Optical studies show that the optical band gap values are 1.25 eV and 1.36 eV for films grown from spray solutions having S/Se ionic ratios 0.4 and 0.6 respectively. The interesting result of this paper is that the optical band gap value (1.25 eV) is very close to the optimum band gap for terrestrial photovoltaic solar energy conversion. The Debye Scherrer formula applied to the XRD patterns show that the average crystallite size of the films is in the range 10 to 20 nm.

Design of the ZnS/Ge/GaSe pn interfaces as plasmonic, photovoltaic and microwave band stop filters

Abstract In the current work, we report and discuss the features of the design of a ZnS (300 nm)/Ge (300 nm)/GaSe (300 nm) thin film device. The device is characterized by the X-ray diffraction, electron microscopy, energy dispersive X-ray spectroscopy (EDS), optical spectroscopy, microwave power spectroscopy and light power dependent photoconductivity. While the X-ray diffraction technique revealed a polycrystalline ZnS coated with two amorphous layers of Ge and GaSe, the hot probe tests revealed the formation of pn interface. The optical spectra which were employed to reveal the conduction and valence band offsets at the ZnS/Ge and Ge/GaSe interface indicated information about the dielectric dispersion at the interface. The dielectric spectra of the ZnS/Ge/GaSe heterojunction which was modeled assuming the domination of surface plasmon interactions through the films revealed a pronounced increase in the drift mobility of free carriers in the three layers compared to the single and double layers. In the scope of the fitting parameters, a wave trap that exhibit filtering properties at notch frequency of 2.30 GHz was designed and tested. The ac signals power spectrum absorption reached ∼ 99%. In addition, the photocurrent analysis on the ZnS/Ge/GaSe interface has shown it is suitability for photovoltaic and photosensing applications.

Plasma measurements in pulse discharge with resistively heated emissive probe

A resistively heated emissive probe has been developed to work in low-pressure air plasma produced by 100 Hz pulsed DC source. The evolution of the discharge and consequent rapid changes in plasma potential and electron temperature are characterized for different fill pressures at constant input voltage of 300 V. The floating point method in the strong emission regime is applied to determine the plasma potential. Emissive probe responds to rapid changes in the discharge current during different stages of the pulse cycle. The electron temperature is determined from the potential difference of hot probe in the strong emission regime and the cold one incorporating the space charge effects of the hot probe. Temporal measurements of Vp and Te describe the development and characteristics of the emissive probe technique for fast measurements in pulsating discharges.

Work Function Estimation of Bismuth Doped ZNO Thin Film

In this paper we report bismuth (Bi) doped ZnO based heterojunction devices. The p-type Bi doped ZnO thin films have been deposited on n and p type silicon substrate using sol-gel spin coating method. The ptype nature of the deposited Bi doped ZnO thin films have been analyzed by hot point probe method. The electrical properties of the fabricated devices have been obtained from I-V characteristic measured using semiconductor parameter analyzer. Finally, the work function of Bi doped ZnO has been estimated from the electrical parameter obtained from I-V calculations.

Nanostructured lipid carriers for the topical delivery of tretinoin

Cosmetic skin care products currently in the market demonstrate an increasing trend toward antiaging products. Selection of the right formulation approach is the key to successful consumer acceptance. Nanostructured lipid carriers (NLCs) for dermal application can render added benefits to the formulation. Tretinoin a derivative of vitamin A, is a retinoid with anti-aging and anti-acne potential. The present study was aimed at formulating NLCs of tretinoin for reducing the skin irritation potential, increasing the drug loading capacity and prolonging the duration of action. The NLCs were optimized using the response surface methodology based on the particle size. Preliminary study, suggested the use of stearic acid, oleic acid, Tween 80 and Span 60 as solid lipid, liquid lipid and surfactants respectively formed a stable dispersion. NLCs of tretinoin were prepared by hot melt microemulsion and hot melt probe sonication methods. The properties of the optimized NLCs such as morphology, size, Zeta potential, stability and in vitro drug release were investigated. Tretinoin loaded NLCs in carbopol gel showed a sustained release pattern with isopropyl alcohol as the receptor fluid compared to the marketed gel using Franz diffusion cells. Eight prepared gel formulations tested were found to follow the Higuchi model of drug release. Stability studies indicated that the formulations stored at refrigeration and room temperature showed no noticeable differences in the drug content and release profiles in vitro, after a period of 4 weeks. In vivo skin irritation test on male Wister rats indicated no irritation or erythema after application of the NLCs loaded gel repeated for a period of 7 days compared to the application of marketed tretinoin gel which showed irritation and slight erythema within 3 days. The results showed that the irritation potential of tretinoin was reduced, the drug loading was increased and the drug release was prolonged by the incorporation into the NLCs.

Optical and electrical characterization of BixSe1−x thin films

Abstract Bulk samples of the BixSe1-x system with (x = 0, 5, and 10) were prepared using conventional melt quenching technique. Thin films were then deposited by thermal evaporation technique under high vacuum conditions from the prepared bulk samples. Effect of Bi substitution on surface morphology, electrical and optical properties of BixSe1-x thin films was studied. X-ray diffraction studies showed the formation of nanocrystalline clusters at Bi concentration x = 10. Formation of these clusters resulted in a rough surface which was confirmed by AFM measurements. The film surface was smooth, with RMS roughness of 0.0124 nm for Bi5Se95. For Bi10Se90, the RMS roughness increased to 3.93 nm indicating the formation of Bi2Se3 clusters. A simple hot probe technique showed a transition from p-type to n-type due to Bi incorporation. Charge transport mechanisms were investigated by temperature dependent DC electrical conductivity measurements in the temperature range of 209 K to 313 K. Electrical activation energy (ΔE) of the films with different Bi concentrations was found to exhibit a notable change at the p to n transition. At low temperature, the conduction was in reasonable agreement with Mott’s condition of variable range hopping. Mott parameters and the density of localized states near Fermi level were evaluated and correlated with the structural changes resulting from Bi addition. In addition, a red shift of the optical absorption edge of the films under study caused by Bi-Se substitution was observed. Slight changes in the optical parameters were observed with the γ-irradiation. Addition of Bi atoms could be used to tailor the structural, electrical and optical properties of chalcogenide materials such as junctionless photovoltaic devices.

On the preparation of n-type SnS:Cu using chemical spray pyrolysis for photovoltaic application: Effect of annealing

Thin films of n-type copper doped tin sulfide (SnS:Cu) are deposited employing Chemical Spray Pyrolysis (CSP) technique and effect of post deposition annealing of the films in vacuum as well as in air is evaluated. Structural characterization through X-ray diffraction proved that annealing aided formation of polycrystalline films with orthorhombic structure and preferential orientation of grains along (111) plane, a direction greatly advantageous for PV applications. Raman spectrum of the films had two peaks (at 96cm−1 and 224cm−1) belonging only to that of SnS. The band gap of as-prepared films is around ~1.5eV which changed slightly on annealing. Surface analysis of SnS:Cu films using atomic force microscopy showed the roughness of vacuum annealed samples to be much lower than that of air annealed samples and confirming all the films to be crack free and devoid of pinholes. Chemical analyses with X-ray photoelectron spectroscopy gives the binding energies of Sn3d5/2 at 485.5eV and S2p3/2 at 161.1eV, confirming the formation of SnS with Sn2+ and S−2 state. The hot probe measurements revealed their n-type nature, which was affirmed by Hall measurements too. Appreciable hike in conductivity is obtained through Cu-doping; however annealing could not produce any notable effect on conductivity.

Synthesis, characterization and solid-state properties of [Zn(Hdmmthiol)2] $\cdot$ 2H2O complex

The zinc(II) complex with tridentate thiohydrazone ligand have been prepared by metal template reaction. The metal template reaction was used to prepare the zinc (II) complex with tridentate thiohydrazone ligand. The reaction of diacetylmonoxime and, morpholine N-thiohydrazidewith Zn(OAc)2 $\cdot$ 2H2O under reflux yielded the formation of the [Zn(Hdmmthiol )2] $\cdot$ 2H2O complex. The complex was characterized by a combination of protocols including elemental analysis, UV+vis, FT-IR, TG and PXRD. The temperature dependence of the electrical conductivity and the optical property of the [Zn(Hdmmthiol )2] $\cdot$ 2H2O complex is called H2dammthiol was studied. Powder X-ray diffraction (PXRD) method was used to investigate the crystal structure of the sample. The zinc complex was shown to be a member of the triclinic system. The zinc complex was determined to have n-type conductivity as demonstrated in the hot probe measurements. The complex was determined to display direct optical transition with band gaps of 2.52eV as determined by the optical absorption analysis.

Low temperature electrical conductivity and seebeck coefficient of nanostructured CuSe thin films with Ga addition

Electrical conductivity and Seebeck coefficient of nanostructured Ga added p-type CuSe thin films are investigated in the temperature range 6–300 K. The films prepared by vacuum co-evaporation method and characterized by various tools like X-ray diffraction, scanning electron microscopy and energy dispersive analysis of X-rays, for their structural, morphological and compositional studies, have agglomerated grains forming particles of size ranging from about 24 nm to 121 nm and lattice constants a = 4.046 Å and c = 1.717 Å. The analysis of conductivity data suggests Mott's variable range hopping in the range 10–120 K, Seto's grain boundary effect in 120–195 K and Arrenhius' thermal activation in 195–300 K, while Seebeck coefficient data corroborates well with Hall and hot probe observations of p-type conductivity. These films have high conductivity of 903 ± 3% S/m at 300 K with the Fermi level lying ∼6 meV above valence band maximum (VBM) within a direct band gap of 1.99 ± 0.03 eV.

XRD Raman analysis and optical properties of CuS nanostructured film

Raman spectroscopy and X-ray diffraction (XRD) methods were applied to determine the phase composition and crystal quality of CuS nanostructured film grown by spray pyrolysis.The film has polycrystalline structure with preferential growth along the (101) plane. The grain size for the film was found to be lower than 20nm. The very sharp Raman peak around 470cm−1 in the high frequency region was identified as the SS stretching mode of S2 ions at the 4e sites. Other Raman peaks were around 266cm−1, 118cm−1 and 68cm−1 in the low frequency region due to CuS phase. Particles of nanometric size show low wavenumber vibrational modes that can be observed by Raman spectroscopy. Optical properties were obtained from UV–vis absorption, transmittance and reflectance spectra of the nanostructured CuS film. The optical constants of the film such as refractive index, extinction coefficient and, optical conductivity were investigated. The film was found to be p-type by using hot probe method.

Temperature dependence of thermal conductivity of vegetable oils for use in concentrated solar power plants, measured by 3omega hot wire method

Following the growing need for innovative heat transfer fluids in concentrated solar power (CSP) plants, the thermal conductivities of different vegetable oils (rapeseed, soybean, sunflower, palm, copra, cotton and jatropha) were measured in the temperature range from ambient to 230 °C relative to a reference oil. The small differences in the obtained thermal conductivities are influenced by the fatty acid composition. For balanced saturated/unsaturated fatty acids composition, the average thermal conductivity decreases from 0.167 Wm−1K−1 at 20 °C to 0.137 Wm−1K−1 at 230 °C. The use of a reference synthetic oil makes the calibration of the thermal probe unnecessary. The used method is based on a hot wire thermal probe with ac excitation and 3ω lock-in detection and has a long-term relative error of 1.2% and absolute accuracy of 2%. It allows measuring in real-time, continuously and independently, the thermophysical properties of oils for thermal applications.

Structural and Morphological Properties of Electrochemically Deposited CdTe Thin Films

In present report, p-type CdTe semiconductor thin films were grown directly on transparent conductive Fluorine-doped SnO2-coated (FTO) glass substrates using three-electrode electrodeposition technique. The whole work carried out at ambient condition. Structural studies reveal that films are possessing cubic zinc blend crystal structure. The growth mechanism of CdTe nanostructures is revealed by investigating the cyclic voltammetry analysis. Morphological characterization demonstrates high-purity, uniform and well covered CdTe thin film over FTO glass substrate. The Hot probe experiment confirmed the p-type semiconducting behavior of CdTe thin films. The current investigation provides a novel approach in synthesis of p-type CdTe nanostructure, without any post annealing or surface treatment, for the direct fabrication of semiconductor sensitized solar cells.

Ultrasonic spray-pyrolyzed CuCrO2 thin films

In this paper the optical, structural and electrical properties of CuCrO2 thin films deposited by ultrasonic spray pyrolysis at temperatures from 400 to 600 °C in steps of 50 °C are presented. Copper and chromium acetylacetonates were chosen as sources of Cu and Cr, respectively, and N,N-dimethylformamide was used as the solvent. X-ray results confirmed that the films as deposited showed the CuCrO2 phase without any post-deposition thermal annealing. The surface morphology was observed to be mirror like, and as the films were deposited at different temperatures, they gradually revealed the presence of small crystallites. The best film’s optical percentage transmission (in the visible region), about 58%, was obtained in films deposited at 450 °C, and the highest band gap energy (3.17 eV) was measured in films deposited at 400 °C. The electrical properties of the films were obtained by the Hall effect. A hole concentration in the range 1019–1021 cm−3, conductivity as high as 35 S cm−1, and mobility lower than 1 cm2 V−1 s−1 were obtained in the films. p-type conductivity was confirmed using the hot point probe arrangement, and the Seebeck coefficient was estimated. The hole conductivity is thought to be due to excess oxygen in the films. Finally, the minimum energy required to transfer carriers from acceptor level to the valence band in the films was estimated by impedance spectroscopy.

Improved Optical Properties of Tin Antimony Sulphide Thin Films for Photovoltaics

Tin antimony sulphide thin films have been synthesized as an absorber layer for solar cells. These films are deposited by vacuum thermal evaporation on glass substrate at a pressure of 10-5 torr. The films are then annealed at different temperatures in argon atmosphere. XRD analysis reveals that both as deposited and annealed films are found to be in polycrystalline phase. The crystallinity of the films is significantly enhanced with increasing annealing temperatures. The quantum efficiency is higher in the visible and near infrared region for the annealed films whereas the quantum efficiency of as deposited film is comparatively lower. The transmittance of the annealed films is found to be decreasing with increasing temperatures. The thickness and band gap of the films are measured by ellipsometric data. The absorption coefficient of the films is significantly higher (~105cm-1), which is very important factor regarding solar conversion efficiency. Hot point probe measurements show that the films possess n-type electrical conductivity.

A Simple and Portable Setup for Thermopower Measurements.

Thermoelectric energy conversion technology has received significant attention because of its promising applications and environmentally clean nature. The innovative design of efficient thermoelectric materials is assisted by simple and reliable techniques for fast and accurate testing. Here, a simple approach for rapid measurement of the Seebeck coefficient is described using commonly available materials based on hot and cold probes; both probes are heated by built-in microheaters. A spring-loaded sample mounting arrangement provides easy sample loading/unloading. The setup is suitable for measurements on a wide range of materials, such as pellets, films, and even soft surfaces without damage. Several known thermoelectric materials, such as alumel, bismuth, and silicon, yielded values close to reported ones. The setup is very compact, simple, fast, low cost, and reliable to develop as a laboratory characterization tool.

Co-rotating vortex interaction

Purpose The purpose of this paper is to study the structure and dynamic development of a pair of co-rotating trailing vortices, during their formation, interaction and merging, using detailed experimental measurements of the velocity and vorticity fields. Design/methodology/approach The vortices were generated using two half wings (NACA0030) positioned at equal and opposite angles of attack at the entrance of the test section of an open-circuit, subsonic, wind tunnel. Velocity vector measurements were obtained at Rec = 133,000, on cross-plane grids at several distances from the trailing edges of the wings, using an in-house developed four-sensor hot wire anemometer probe. Findings The results include cross-plane contour plots of the mean and fluctuating velocity as well as mean vorticity fields. Each of these variables is affected in a different way, providing complementary information on the development of the flow field. After shedding, the two vortices are swept along the stream-wise direction and spiral around each other, thereby developing a braid of two vortices, which then deforms the external flow field. Gradually, the interaction with the external flow field links both vortices together until the final merging and the formation of a new stable linear vortex emerges. Practical implications Trailing vortices have been rendered particularly important during the past decades, because of increasing traffic density of very heavy aircrafts and several plane “incidents”, which were attributed to the action of the vortex wake. Originality/value The presented results provide information on the evolution and merging of a pair of vortices formed by a closely spaced differential wing configuration. The vortices interact almost immediately after shedding as expected in flap–flap or flap–wing vortices interaction.