Electrical Properties Of Amorphous Films Research Articles

Electrical properties of amorphous films and crystallization of Li–Nb–O system on silicon

Li–Nb–O amorphous films were deposited onto Si substrates by the radio-frequency magnetron sputtering method in an Ar environment. As-grown films are crystallized under thermal annealing (TA) at the temperature of up to 600 °C with a formation of LiNbO3. Capacitance–voltage and current–voltage analysis revealed a positive fixed oxide charge existed in the films. TA influences the structure and electrical properties of as-grown films. The fraction of a crystalline phase in the film increases from 45 to 100% when raising the annealing temperature from 450 to 475 °C. The effective positive charge in the amorphous films changes non-monotonically with TA reaching a minimum value at the temperature of 450 °C when the effective dielectric constant has a maximum value. The concentration of traps in the films depends on the annealing temperature and reaches a minimum value at T = 600 °C which is caused by the formation of the large-block crystalline structure. Charge transport mechanisms are also discussed.

Correlation between Optical and Electrical Properties of the Pulsed-Laser Deposited Amorphous Films of Germanium

Amorphous films of germanium (thicknesses 25 - 450 nm) were obtained on glass substrate at room temperature by the vacuum (residual gas pressure 3´10-6 mm Hg) pulsed-laser (Q-switched glass: Nd3+ laser (1.064 µm wavelength, 30 ns pulse duration, laser energy - 3 J per pulse, laser intensity on Ge target ~109 W/cm2)) deposition method. The comprehensive study of the optical and electrical properties of amorphous films of germanium showed the presence of two types (A and B) of films with different characteristics. With increasing of film thickness from 100 nm to 450 nm we observe the transition from the prevailing topological disorder (A- type) to the quantify disorder (B- type) in the region of 300-350 nm. Thicker films are characterized by a more homogeneous “network” of bonds, which minimizes the number of defects and localized states in the “forbidden” gap and, consequently, increases the resistivity and optical gap. An increase of the resistivity and optical gap is observed with decreasing film thickness (< 100 nm), which is explained by an increasing influence of natural oxidation of thin films. The results of temperature measurements for A- type films shows that the temperature dependence of resistivity is characterized by Mott's law (lnρ ~ T-1/4) in the temperature range of 100-240 K, while for B- type it indicates an activation character (lnR ~ ΔEa/kT) in the temperature range of 150-350 K.

The Effect of Oxygen on Amorphous Films of ZnTe

It has been found that oxygen plays an important role in determining the electrical properties of amorphous films of ZnTe. The effects produced by oxygen chemisorption have been studied and reproducible films of amorphous ZnTe (a-ZnTe) have been produced. Thus it is believed that electrical measurements performed on these films will be helpful in determining the conduction processes in them and may lead to a better understanding of the amorphous state in general.

Electrical properties of amorphous films of TeTl alloys

Amorphous films of TeTl alloys have been prepared with compositions in the range 20–70% Tl either by co-evaporation of the constituent elements or by a modification of the flash evaporation method. Measurements were made of the conductivity as a function of both composition and temperature. The conductivity of the as-deposited alloys plotted as a function of composition shows minima at Tl 2Te n ( n = 1–7) and at Tl 3Te 2 and Tl 5Te 3; at each of these compositions there is a maximum in the activation energy versus composition plot. A band structure model that could explain the electrical properties of these films is given.