Muhammet Yildirim

Growth and Temperature Dependence of Optical Properties of Er Doped and Undoped n-Type InSe

n-InSe and Er doped n-InSe (n-InSe:Er) single crystals were grown by the modified Bridgman-Stockbarger method. The prepared InSe and InSe:Er single crystal ingots were 12 mm in diameter and about 80 mm in length. The ingots had no cracks or voids on the surface. The absorption measurements were carried out for n-InSe, and n-InSe:Er samples in the temperature range of 10–320 K. Binding energies of n-InSe and n-InSe:Er were calculated to be 20.5 meV and 21.0 meV respectively. The direct band gaps were estimated to be 1.339 eV, 1.289 eV and 1.256 eV in n-InSe and were 1.338 eV, 1.288 eV and 1.253 eV in n-InSe:Er at 10 K, 200 K and 300 K, respectively. Eo (1.247 eV) obtained from the Urbach rule is nearly equal to the energy gap of n-InSe at 300 K.

Electric field influence on absorption measurement in InSe single crystal

Abstract InSe single crystal was grown by Bridgman–Stockberger method. Electric field effect on the absorption measurements have been investigated as a function temperature in InSe single crystal. The absorption edge shifted towards longer wavelengths and a decrease of intensity in absorption spectra occurred under an electric field of 5 kV / cm . Using absorption measurements, steepness parameter and Urbach energy were calculated under electric field. Applied electric field caused an increase in the Urbach energy. At 10 and 320 K , the first exciton energies were calculated as 1.350 and 1.311 eV for zero voltage and 1.334 and 1.301 eV for electric field respectively.

Growth and optical properties of Ho doped n-type indium selenide

n-InSe and Ho doped n-InSe (n-InSe:Ho) single crystals were grown by a method which is similar to the direct freezing method. The crystals used in this study were grown in our crystal growth laboratory. The ingots had no cracks and voids on the surface. There was no process to polish and clean the samples because of the natural mirror-like cleavage faces. The X-ray Laue back-reflection method was used to test the crystallinity of the prepared sample. The absorption measurements were carried out in n-InSe:Ho sample in the temperature range from 10 to 320 K. The exciton energies for n = 1 were calculated as 1.315, 1.302, 1.266 and 1.238 eV in n-InSe:Ho at 10, 100, 200 and 280 K, respectively. The exciton energies for n = 2 in n-InSe:Ho are 1.328, 1.322, 1.318 at 10, 60 and 80 K, respectively. The exciton binding energy of n-InSe:Ho was calculated as 17.3 meV. The direct band gaps for n-InSe:Ho are 1.332, 1.313, 1.283 and 1.255 eV at 10, 100, 200, 280 K, respectively.

Absorption measurements in InSe:Ho single crystal under an electric field

InSe:Ho single crystal was grown by Bridgman-Stockberger method. Electric field effects on the absorption measurements have been investigated as a function of temperature in InSe:Ho single crystal. The absorption edge shifted towards longer wavelengths and a decrease of intensity in absorption spectra occurred under an electric field of 7.5 kV/cm. Using absorption measurements, steepness parameter and Urbach energy were calculated under electric field. Applied electric field caused an increase in the Urbach energy. At 10 K and 320 K, the first exciton energies were calculated as 1.322 and 1.301 eV for zero voltage and 1.245 and 1.232 eV for applied electric field, respectively.

Barrier height enhancement by annealing CrNiCo alloy Schottky contacts on LEC GaAs

Abstract The Schottky barrier height and ideality factor of CrNiCo alloy Schottky contacts on a n -GaAs substrate have been measured using a current-voltage (I−V) technique after different rapid thermal annealings (RTA) for 20 s in a vacuum of ≈10 −5 torr (temperature range from 299 to 900 K). The value of barrier height Φ b and ideality factor n range from 0.57 eV at 1.14 (at room temperature) to 0.67 eV and 1.00 (at 673 K). Nonideal values of Φ b and n are attributed to the presence of an interfacial layer between the alloy and the semiconductor interface. However, the value of 1.00 for n at 673 K shows that annealing up to this temperature causes a disapperance of the I − V nonidealities. The fact that the barrier height increases and the ideality factor decreases to unity is ascribed to reduction of the interfacial oxide layer by metal Cr. On the other hand, the contact properties of the Schottky diodes deteriorated and became nearly ohmic when the annealing temperature reached 900 K for 20 s. This showed that there are not sufficient quantities of nickel in our CrNiCo alloy. The excellent saturation of the reverse bias curves which are due to the smoothness and quality of the metal/GaAs interface (even with annealing to a high temperature) are attributed to the existence of Co in the alloy.

A comparison study of Co and Cu doped MgO diluted magnetic thin films

Transition metal-doped MgO diluted magnetic thin films are appropriate candidates for spintronic applications and designing magnetic devices and sensors. Therefore, MgO:Co and MgO:Cu films were deposited on glass substrates by Chemical Spray Pyrolysis (CSP) method different thin film deposition parameters. Deposited different transition metal doped MgO thin films were compared in terms of optic and structural properties. Comparison optic analysis of the films was investigated spectral absorption and transmittance measurements by UV-Vis double beam spectrophotometer technique. Comparison structural analysis of the thin films was examined by using XRD, Raman Analysis, SEM, EDX and AFM techniques. The transition metal-doped; MgO:Co and MgO:Cu thin films maybe have potential applications in spintronics and magnetic data storage.

Electrical characterization of In/p-GaSe:Cd/Au–Ge single crystal grown by Bridgman/Stockbarger method

The temperature dependence of current–voltage (I-V) characteristics of Au–Ge/p-GaSe:Cd Schottky diode (SD) has been investigated in the temperature range of 40–360 K with a temperature step of 10 K under dark conditions. The characteristic parameters of the SD such as barrier height, ideality factor and series resistance have been determined from the I-V measurements. It has been shown that the ideality factor increases while the barrier height decreases with decreasing temperature. The values of series resistance obtained from modified Norde’s function. Series resistance values increase with decreasing temperature.

Effect of copper and nickel doping on the optical and structural properties of ZnO

The present study is focused on the Cu doped ZnO and Ni doped ZnO dilute magnetic semiconductor thin films. ZnO:Cu and ZnO:Ni thin films were grown by Chemically Spray Pyrolysis (CSP) method on glass substrates. Optical analysis of the films was done spectral absorption and transmittance measurements by UV-Vis double beam spectrophotometer technique. The structure, morphology, topology and elemental analysis of ZnO:Cu and ZnO:Ni dilute magnetic thin films were investigated by X-ray diffraction (XRD), Raman Analysis, field emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDX), atomic force microscopy (AFM) techniques, respectively. Also The magnetic properties of the ZnO:Ni thin film was investigated by vibrating sample magnetometer (VSM) method. VSM measurements of ZnO:Ni thin film showed that the ferromagnetic behavior.

Exciting transition metal doped dilute magnetic thin films: MgO:Er and ZnO:Er

Erbium doped MgO and doped ZnO thin films have reasonably important properties applications in spintronic devices. These films were synthesized on glass substrates by Chemical Spray Pyrolysis (CSP) method. In the literature there has been almost no report on preparation of MgO:Er dilute magnetic thin films by means of CSP. Because doped thin films show different magnetic behaviors, depending upon the type of magnetic material ions, concentration of them, synthesis route and experimental conditions, synthesized MgO:Er and ZnO:Er films were compared to thin film properties. Optical analyses of the synthesized thin films were examined spectral absorption and transmittance measurements by UV-Vis double beam spectrophotometer technique. Structural analysis of the thin films was examined by using XRD, Raman Analysis, FE-SEM, EDX and AFM techniques. Also, magnetic properties of the MgO:Er and ZnO:Er films were investigated by vibrating sample magnetometer (VSM) which show that diamagnetic behavior of the MgO:Er ...

Magnetic, optical and structural characterization of ZnO:Co; ZnO:Fe thin films

Co-doped ZnO and Fe-doped ZnO diluted magnetic semiconductor films were prepared on glass substrates by chemical spray pyrolysis (CSP) method. Synthesized ZnO:Co and ZnO:Fe thin films by CSP method were compared to thin film properties. Optical analysis of the synthesized thin films was examined by spectral absorption and transmittance measurements using UV-Vis double beam spectrophotometer technique and Photoluminescence (PL) spectroscopy. Structural characterizations of the thin films were examined by using X-ray diffraction (XRD), Raman Analysis, field emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDX) and atomic force microscopy (AFM) techniques, respectively. Magnetic properties of the films investigated by Vibrating sample magnetometer (VSM) measurements and magnetization measurements of thin films were compared.VSM measurements of ZnO:Co and ZnO:Fe thin films showed that ferromagnetic behavior for each thin films.