Jamal Takadoum

Enhanced sputtering of titanium oxide, nitride and oxynitride thin films by the reactive gas pulsing technique

The reactive gas pulsing technique was used to deposit titanium oxide, nitride and oxynitride thin films by d.c. reactive magnetron sputtering. A pure titanium target was sputtered in a mixture of Ar + O 2 for TiO x , Ar + N 2 for TiN y and Ar + O 2 + N 2 for TiO x N y . The reactive gas was injected with a well-controlled pulsing method for titanium oxide and nitride whereas titanium oxynitride were prepared with a constant flow rate of nitrogen and a pulsing flow rate of oxygen. A constant pulsing period was used for every deposition and the injection time of the reactive gas was systematically changed. Instability phenomena typical to the reactive process were prevented by this technique. An improvement of the deposition rate of TiO 2 and TiN thin films was achieved. The modulation of the reactive gas injection time allowed to change the crystallographic structure of the material as well as the chemical composition (1.4 <x < 2.0 for TiO x and 0.45 < y < 1.06 for TiN y ). With two reactive gases, the pulsing technique appeared as an original way to prepare titanium oxynitride with every x, y composition. Real time measurements of the Ti target potential were used as process parameters in relation to the changes in TiO x , TiN y and TiO x N y thin film properties.

Multi-asperity Nanotribology of Self-Assembled Monolayers Grafted on Silicon Wafers Displaying Various Crystallographic Orientations and Nanostructures

Micro/nanotribological study of self-assembled monolayers (SAMs) derived from n-alkyltrichlorosilanes deposited on silicon wafers displaying various crystallographic orientations—Si (100), Si (111) and Si (110)—has been conducted using a ball-on-disc nanotribometer. The parameters that have been varied are (i) the alkyl chain length, (ii) the tribological parameters (i.e. the normal load, the sliding velocity, the sliding distance and the relative humidity level) and (iii) some surface characteristics of the silicon substrates (i.e. crystallographic orientation, roughness, and thickness of the amorphous native oxide). Experimental results show that the key parameter controlling the tribological behaviour is not the alkyl chain length as generally reported for adsorbed and grafted monolayers, but rather the film’s homogeneity—i.e. the degree of packing and the surface coverage of the monolayer—in connection with the crystallographic orientation of the substrate.