Tilt angle control of nanocolumns grown by glancing angle sputtering at variable argon pressures

Abstract

We show that the tilt angle of nanostructures obtained by glancing angle sputtering is finely tuned by selecting the adequate argon pressure. At low pressures, a ballistic deposition regime dominates, yielding high directional atoms that form tilted nanocolumns. High pressures lead to a diffusive regime which gives rise to vertical columnar growth. Monte Carlo simulations reproduce the experimental results indicating that the loss of directionality of the sputtered particles in the gas phase, together with the self-shadowing mechanism at the surface, are the main processes responsible for the development of the columns.

Influence of plasma-generated negative oxygen ion impingement on magnetron sputtered amorphous SiO2 thin films during growth at low temperatures

“…3(d). 16,22 Indeed, the growth of the film at the backside of the substrate holder takes place by the incorporation of Si sputtered atoms that have been (nearly) thermalized due to scattering processes in the plasma. This assumption is reasonable since, in average, only two collisions between sputtered Si and Ar atoms are required in order to lose the initial preferential directionality of the former.…”

“…Conversely, the surface shadowing mechanism, determined by the directionality of the sputtered particles arriving at the film, is a relevant process by which taller film surface features prevent the deposition under their shadow. 22 According to the structure zone model (SZM), the value of the ratio T s =T m (the so-called homologous temperature), where T s is the film temperature during growth and T m the melting temperature, gives information on the relevance of surface shadowing in comparison with thermally activated diffusion processes during growth. 23 In this way, when T s =T m is approximately below 0.3 (the socalled Zone I), the SZM indicates that surface shadowing dominates over thermally activated diffusion processes.…”

Nanocolumnar growth of thin films deposited at oblique angles: Beyond the tangent rule

“…An implicit assumption in these rules is that the relation between  and  is purely geometrical and, thus, independent of the nature of the deposited material, a hypothesis that can be considered doubtful for most conditions. 29 In reference 30, following similar philosophy than in previous works, [31][32][33][34] we developed a Monte Carlo ballistic model to describe the PVD deposition of thin films at oblique angles and at low temperatures. In that work, we proposed that short-range interactions between vapor species and the film surface could influence the film growth through a so-called surface trapping mechanism.…”

Preventing bacterial adhesion on scaffolds for bone tissue engineering

“…It is based on exploiting atomic shadowing effects during physical vapor deposition under high vacuum conditions. In this sense, the main processes responsible for the formation of the nanostructures are the atomic self-shadowing mechanism at the surface and the collisional processes of the sputtered atoms in the plasma phase, mediated by the tilt angle of the substrate and the value of the argon background pressure [65] . Figure 3A indicated SEM micrographs corresponding to Ti6Al4V substrates before and after (Nano-Ti6Al4V) MSGLAD processing, displaying different topological surface features.…”