Yilmaz, Mehmet; Kocyigit, Adem; Cirak, Burcu Bozkurt; Kacus, Hatice; Incekara, Umit; Aydogan, Sakir

We employed hematoxylin as interfacial layer between the n- and p-type silicon substrate and cobalt (Co) metallic contact to obtain and compare Co/hematoxylin/n-Si and Co/hematoxylin/p-Si devices for a wide range temperature via current-voltage (I–V) characteristics. Furthermore, we studied structural and morphological properties of the hematoxylin thin film by x-ray diffractometer (XRD) and scanning electron microscope (SEM). The temperature range was changed from 100 K to 460 K via 20 K interval for I–V measurements. The Co/hematoxylin/n-Si and Co/hematoxylin/p-Si devices exhibited excellent rectifying behaviors for low temperatures, but rectifying ratio (RR) values decreased with increasing temperature at ±1 V bias. In addition, the devices showed thermal sensor or detector behavior because current values increased with increasing temperature at reverse biases. The Co/hematoxylin/p-Si device has better stability than Co/hematoxylin/n-Si device at reverse biases for the same temperature values according to stop leakage current with increasing voltage. In addition, the diode parameters such as barrier height, ideality factor and series resistance as well as interface states density were extracted from the I–V measurements and compared in details for various techniques such as thermionic emission theory, Norde and Cheung methods. The diode parameters of the both devices were affected from the temperature changes. The Co/hematoxylin/n-Si and Co/hematoxylin/p-Si devices are good candidate for rectifying and thermal sensing applications.

Soltabayev, Baktiyar; Yıldırım, Memet Ali; Ateş, Aytunç; Acar, Selim

In-doped ZnO thin films with 0%,1%, 3%, 5% and 7% In were deposited by Successive Ionic Layer Adsorption and Reaction (SILAR)method on glass substrates for nitric oxide (NO)gas sensing application. X-ray diffraction (XRD), scanning electron microscope (SEM)and energy dispersive X-ray analysis (EDAX)were used to evaluate the effect of In doping concentrations on properties of the films. The XRD study clearly shows the existence of the polycrystalline structure of the films. The morphological study indicates the formation of a uniform particle such as granular and nano-flower structures on the surface of the films. The most important morphological change was observed at 3% indium doped thin film, which has nano-flower surface morphology. The gas sensing measurements were performed for different temperature and different NO gas concentrations. The maximum gas sensitivity was revealed at an optimal indium doping concentration of 3 at.% that achieved the highest sensitivity with a value of 22.4 for 50 ppm NO gas at 167 °C.

Tuzluca, Fatma Nur; Yesilbag, Yasar Ozkan; Akkus, Tuba; Ertugrul, Mehmet

This study investigated the effects of graphite powder on the growth mechanisms of one-dimensional (1-D) single-crystal indium oxide (In2O3) nanostructures. The study was conducted using a chemical vapor deposition (CVD) method at 1000 °C; In2O3 and graphite powder mixed with In2O3, with a weight ratio of 1:1, were used as the source material, while 2 nm-thick n-type silicon (100), coated with a gold catalyst, was used as a substrate. It was observed that nanostructures grew via a Vapor-Liquid-Solid (VLS) growth mechanism when only In2O3 was used, but grew via both VLS and Vapor-Solid (VS) growth mechanisms when graphite powder was used with the In2O3. The morphology and crystal structures of the nanostructures grown were investigated using X-Ray Diffraction (XRD), High Resolution Transmission Electron Microscopy (HR-TEM), Field Emission Scanning Electron Microscopy (FESEM) and Energy Dispersion X-Ray Spectroscopy (EDS). At room temperature (RT), all the nanostructures showed photoluminescence (PL) spectra at a wavelength of 367 nm in the UV-emission region and at wavelengths of 470 and 630 nm in the visible region.

Ejderha, K.; Zengin, A.; Orak, I.; Tasyurek, B.; Kilinç, T.; Turut, A.

We have formed Ni/n-Si SBDs contacts by dc magnetron sputtering Ni on the epitaxy n-type Si. We have introduced the temperature-dependent IV characteristics of the diodes in the temperature range of 60320 K. It has been seen that the BH values for the contacts formed by the evaporating or sputtering the metal are higher than that of the BH values for the contacts formed by the electro-deposition in the literature. The experimental nT versus T curve for the Ni/epitaxy n-Si Schottky diode has corresponded to an average ideality factor value of about 1.55 in the range of 240320 K and to field emission behavior in the range of 60240 K. Furthermore, we also have investigated the dependence of the reverse bias IV characteristics on the applied bias. The reverse bias IV curves computed by considering bias dependence of the BH exactly coincide with the experimental IV curves when the required equation is used in a given temperature. It has been concluded that the existence of BH inhomogeneity and the free carriers tunneling effect may offer the abnormal bias dependence of the experimental soft reverse characteristics.

Ates, Aytunc; Yildirim, M. Ali; Kundakci, Mutlu; Astam, Aykut

Zinc sulphide (ZnS) thin films were grown on glass substrates by the Successive Ionic Layer Adsorption and Reaction (SILAR) technique at room temperature and ambient pressure. Surface morphologies of grown films were characterized using scanning electron microscopy (SEM). The crystal structure and crystal size of the thin films were characterized by the X-ray diffraction (XRD) method and found that the films exhibit polycrystalline characterization. The optical absorption measurements were done as a function of the temperature at 10-320 K temperature range. Using absorption measurements, the band gap energies were calculated at 10 and 320 K, as 3.83 and 3.72 eV, respectively. The annealing temperature effect on optical band gap and the light effect on the electrical properties of ZnS thin films were investigated and it was found that the current increased with increasing light intensity. The annealed films were found have more resistance than the as-grown film.