Aslan Çakir, Mevra

In this study, CrN and ZrN films were coated onto the surfaces of β-type Ti-29Nb-13Ta-4.6Zr alloy (TNTZ), which is used as a biomaterial, using the magnetron sputtering method. The structural and morphological analyses of CrN- and ZrN-coated TNTZ samples were performed with XRD, SEM, EDS, hardness and 3D optical profilometer. In order to determine the wettability and surface free energy properties of untreated TNTZ, CrN- and ZrN-coated TNTZ samples, contact angle measurements were taken with distilled water, hexadecane, ethylene glycol and phosphate-buffered saline (PBS) solutions. The effects of CrN- and ZrN-coated surfaces on friction and wear properties in dry and liquid conditions (PBS) were investigated by magnetron sputtering technique. The sample with the best hydrophobic and oleophobic properties was obtained from ZrN-coated TNTZ. The surface free energy values of the untreated, CrN- and TiN-coated TNTZ samples were measured as 38.20, 34.95 and 28.84 mN/m, respectively. It was determined that CrN- and ZrN-coated TNTZ sample surfaces increased the wear resistance with a protective barrier effect, and the best wear resistance was found in the ZrN-coated TNTZ sample in PBS environment.

Gülnahar, Murat

The rectifying junction properties of an Ag/n-InP Schottky diode are investigated in a wide temperature range from 10 K to 300 K (−263 °C to 27 °C). The electronic structure of the junction is analyzed by the techniques of current–voltage I–V and capacitance–voltage C–V measurement as a function of temperature. The electrical parameters are characterized with the standard thermionic emission theory. The main electrical characteristics including the values of apparent barrier height ϕe and ideality factor n are found to be 0.414 eV and 1.008 at 300 K (27 °C), respectively, even though the value of barrier height ϕb at 300 K (27 °C) from C–V data is 0.417 eV. The ϕe, n, and Richardson plot demonstrate strong temperature dependency; that is, the ϕe decreases, n increases, and the Richardson plot deviates with decreasing temperature. Such behaviors are attributed to Schottky barrier anomalies, which are explained by assuming the existence of a Gaussian distribution of nanometer-sized patches with low barrier height at the interface. The accurate theoretical models such as Tung’s lateral inhomogeneity and multi-Gaussian distribution to comment the barrier inhomogeneity on the electron transport across the interface are applied, and the comparisons between these approaches for the present experimental results are carried out. According to the multi-Gaussian distribution approach, the double-Gaussian nature of Ag/n-InP/In is commented by the values of the weighting coefficients, standard deviations, and mean barrier height calculated for each distribution. The total effective area of the patches NAe is calculated for high and low temperatures, and as a result, it is found that the low barrier regions influence significantly the electron transport at the interface of the junction. The discrepancy between I–V and C–V barrier heights is discussed based on a Gaussian approach. From the linear relationship between ϕe and n, the homogeneous barrier height ϕb is noted to be 0.418 eV. The values of A∗ (effective Richardson constant) and ϕb are determined from classic modified Richardson plot as (Formula presented.) and (Formula presented.): 0.416 eV and from Tung’s model as A∗: 9.35 A cm(Formula presented.) and (Formula presented.): 0.418 eV, which demonstrates an excellent agreement with the theoretical value (9.4 A cm−2 K−2) of n-InP. As a result, in order to obtain the more reliable values of AA∗ and ϕb_, it could be reported that Tung’s lateral inhomogeneity approach is more meaningful; taking into account the effective patch area, which is significantly lower than the whole geometric area of the diode.

Duman, Songül; Ozcelik, Fikriye Seyma; Gürbulak, Bekir; Gülnahar, Murat; Turut, Abdulmecit

The organic methyl green (MG) has been investigated for the first time for its electronic applications. In order to see the effect of organic MG layer on electrical characteristics of Al/p-Si diode, Al/MG/p-Si structure has been fabricated by inexpensive and simple “drop coating” method. The current–voltage (I–V) and capacitance–conductance–voltage (C–G–V) characteristics of Al/SiO2/p-Si and Al/MG/p-Si structures have been investigated. The parameters such as ideality factor (n), barrier height , series and shunt resistance, and the density of interface states have been investigated using current–voltage measurements, in dark and under illumination conditions at room temperature. The n and value of the Al/SiO2/p-Si structure at room temperature is larger than that of conventional Al/p-Si diode. It is seen that the n value of 1.36 calculated for the Al/MG/p-Si structure is lower than most of the metal/organic compound/inorganic semiconductor devices.

Kara, Levent; Küçükömeroǧlu, Tevfik; Baran, Özlem; Efeoǧlu, Ihsan; Yamamoto, Kenji

Structure and adhesion properties of TiAlCrNbN coatings were investigated. These coatings were deposited onto AISI H13 steel substrate using pulsed dc closed field unbalanced magnetron sputtering at different deposition parameters including duty cycle, bias voltage, and working pressure. The coatings have been characterized by X-ray diffraction, scanning electron microscopy and energy dispersive spectroscopy. The TiAlCrNbN-graded composite coatings have a dense and columnar structure. The X-ray diffraction patterns of coatings exhibited predominantly c-TiAlCrN, h-NbN, and h-TiAlN reflections. Scratch resistance test showed that the highest adhesion strength was attained as 68 N at 2.5 μs duty time, 100 V bias voltages, and 3 × 10-3 Torr deposition parameters. The lowest adhesion strength was obtained as 55 N at 0.5 μs duty time, 50V bias voltage, and 2 × 10-3 Torr deposition parameters.