AlN thin films deposited by a hybrid plasma system

Abstract

A hybrid plasma resulting from a combination of a stationary microwave electron cyclotron resonance (with magnetic field) discharge, and a pulsed laser ablation plasma was used to deposit aluminum nitride (AlN) thin films. The hybrid plasma was created at a working pressure of 8 × 10−2 Pa in nitrogen atmosphere. The use of the hybrid plasma allowed efficient laser ablation at low working pressures. Different samples were grown varying the laser power density deposited on the aluminum target. The variation of this power produced ions with different mean kinetic energy (Ek) in the laser ablation plasma. The values of the mean kinetic ion energy were determined using a Langmuir planar probe and were used as the working parameter. The composition of the AlN thin films was measured using the XPS technique. These measurements showed that most of the bonds between Al and N corresponded to that of the AlN compound and their amount increases with Ek. The bandgap of the samples was determined as a function of Ek and was observed to vary between 5.4 and 6 eV. Nano indentation measurements showed a variation of the hardness between 23 and 30 GPa as a function of Ek. The wear rate and friction coefficient were evaluated on samples deposited under different values of Ek, using a reciprocating tribometer.