Güven Çankaya

Schottky Barrier Height Dependence on the Metal Work Function for p-type Si Schottky Diodes

We investigated Schottky barrier diodes of 9 metals (Mn, Cd, Al, Bi, Pb, Sn, Sb, Fe, and Ni) having different metal work functions to p-type Si using current-voltage characteristics. Most Schottky contacts show good characteristics with an ideality factor range from 1.057 to 1.831. Based on our measurements for p-type Si, the barrier heights and metal work functions show a linear relationship of current-voltage characteristics at room temperature with a slope (S=ϕb/ϕm) of 0.162, even though the Fermi level is partially pinned. From this linear dependency, the density of interface states was determined to be about 4.5 · 1013 1/eV per cm2, and the average pinning position of the Fermi level as 0.661 eV below the conduction band

Reverse bias capacitance-voltage characteristics of Au/n-GaAs Schottky diodes under hydrostatic pressure

In Au/n-GaAs Schottky diodes, a remarkable decrease in the depletion layer capacitance was observed by application of hydrostatic pressure. The capacitance decrease induced by the hydrostatic pressure is attributed to the change of ionized additional donor-like defect centres. Since the capacitance decrease is due to hydrostatic pressure, we suggest an application as a pressure-sensitive capacitor.

The Temperature Dependence of Work-Hardening Rate in Invar Fe–Ni Alloys

The stage I work-hardening behavior of Invar Fe-Ni alloys was studied in tension in the temperature range from room temperature to 700 K. Work-hardening rate (WHR) is a function of temperature and has a peak at about 560 K. The anomalous strength is attributed to thermally activated cross-slip.

Frequency dependence of capacitance of Au/n-GaAs Schottky diode under hydrostatic pressure

Au/n-GaAs Schottky barrier diodes have been fabricated and the characteristics of capacitance versus frequency under hydrostatic pressure and forward bias were investigated. Although the capacitance is independent of frequency over 50 kHz, it was found that the capacitance strongly depends on forward bias and hydrostatic pressure due to a change of ionized defect concentration in the low-frequency region. These pressure-dependent studies may be of importance for the application of this material as a pressure-sensitive capacitor.

Effect of Indentation on I-V Characteristics of Au/n-GaAs Schottky Barrier Diodes

Au/n-GaAs Schottky barrier diodes (SBDs) have been fabricated. The effect of indentation on Schottky diode parameters such as Schottky barrier height (φb) and ideality factor (n) was studied by current-voltage (I-V) measurements. The method used for indentation was the Vickers microhardness test at room temperature. The experimental results showed that the I-V characteristics move to lower currents due to an increase of φb with increasing indentation weight, while contacts showed a nonideal diode behaviour.

STEADY-STATE CREEP DEFORMATION OF Cd SINGLE CRYSTALS

The creep behaviour of Cd single crystals has been investigated in tension in the temperature range from 300 Κ to 450 K. The activation energies and the stress exponents of steady-state creep were calculated. The dependence of steady-state creep rate on the stress and temperature show a possible change in the rate-controlling mechanism for creep.

The Effect of Crystal Diameter and Orientation On Plastic Deformation in White Tin Single Crystals

The stress-strain curves of white tin single crystals have been determined as a function of crystal diameter and orientation at room temperature. The stress-strain curves, especially for thinner crystals, are characterized by a remarkable decrease in stress after yielding followed by a gradual increase in the stress with strain due to work hardening. On the other hand, the easy glide region was found to be a function of both crystal diameter and orientation.

Deformation Twinning in Cd Single Crystals

Deformation twinning in hexagonal-close-packet (Lc.p.) crystals has been investigated under tension at room temperature. It was found that deformation twinning is possible in Cd single crystals at room temperature. But twinning was observed only in a limited number of crystallographic orientations, and twinning stress changed according to these orientations.