Nickolash Kasch, Alexander Topping, Power Roll Limited, Murton, United Kingdom
PowerRoll’s technology uses a pre-patterned substrate to produce functioning flexible electronics at high throughput. The key technique enabling this is the physical vapour deposition of successive layers with the source placed at an angle with respect to the substrate plane, so that shadowing effects in the substrate pattern allow the depositions to be selective on a microscopic scale. Opposite to what is desired in most other applications, this requires the deposition to be somewhat ‘directional’ rather than conformal. Here we examine with the aid of a simple model under what circumstances layers deposited by magnetron sputtering will meet this condition. This work is helping us to understand how we can widen the process window we can work with, giving ourselves the strongest opportunity to meet the specifications needed for applications of our technology. We specifically use examples of Power Roll solar development to illustrate the resultant coating produced well beyond the mean free path of ballistic travel at sputtering pressures.