Scanning force microscopy of plasma polymerised hexane: information on themechanical properties of thin films from tip-induced wear

Scanning force microscopy has been used in contact mode to induce wear of t hin plasma polymerised hexane (ppHex) films. The extent of wear observed ca n be used to qualitatively assess the mechanical properties of such thin fi lms. The wear-resistance of the ppHex films varies greatly with the deposit ion power. They are harder than conventional polymers when deposited at hig h power and considerably softer when deposited at low power. On continued s canning, the morphology of the ppHex films is modified, leading to the form ation of two parallel ridges that gradually merge into one larger central r idge. This behaviour differs significantly from that observed on tip-induce d wear of conventional polymer films where patterns of many ridges and trou ghs often form. Tip-induced wear was more extensive at higher applied load, lower scan rate and at higher scan line densities. The scan speed dependen ce is different from that observed for conventional polymers, and may be ex plained in terms of the viscoelastic behaviour of the materials. (C) 2000 E lsevier Science Ltd. All rights reserved.