Effect of Alternating Electric Field Modulation on Liquefaction of Chromium Thin Film

A plethora of factors are known to affect the electric field assisted liquid material formation process on nanometer thick chromium (Cr) films. Among electrical parameters, apart from the magnitude of the applied voltage signal, the frequency of applied alternating current (AC) signal is also known to play a massive role in the process. Venturing into modulating the applied AC signal, varying different AC signal parameters could help us achieve better control over the entire phenomenon. AC modulation affects the net impulse experienced by the various ions in play and thereby affects the net areal spread of the liquified region up to three times. Square wave signals of different frequencies are used for this study. Keeping the peak negative voltage level of the AC signal fixed at −10 V and varying the peak positive voltage from 2.5 V to 10 V, results in the extent of material formation almost doubling. Varying the duty cycle of the square signal over a large scale showed non-linear trends, which led us to investigate the dominance of one half of a full cycle over the other. The negative part of an entire time cycle is found to be more dominant than its counterpart. The observations made in this study helped us to gain significant insights into the mechanism behind this phenomenon, which revealed an ionic transport process to be the controlling factor. We show that AC signal modulation can be used in confining the material formation process observed on Cr thin films. This will help us in controlling a novel scanning probe based lithography (SPL) process – electrolithography, which uses the above-mentioned phenomenon as the central step.