On the microstructure of thin films grown by an isotropically directed deposition flux

Abstract

Articles you may be interested inThe influence of isotropically directed deposition flux on the formation of the thin film microstructure at low temperatures is studied. For this purpose we have deposited TiO 2 thin films by two different deposition techniques: reactive magnetron sputtering, in two different experimental configurations, and plasma enhanced chemical vapor deposition. The obtained results indicate that films grown under conditions where deposition particles do not possess a clear directionality, and in the absence of a relevant plasma/film interaction, present similar refractive indices no matter the deposition technique employed. The film morphology is also similar and consists of a granular surface topography and a columnarlike structure in the bulk whose diameter increases almost linearly with the film thickness. The deposition has been simulated by means of a Monte Carlo model, taking into account the main processes during growth. The agreement between simulations and experimental results indicates that the obtained microstructures are a consequence of the incorporation of low-energy, isotropically directed, deposition particles.

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

“…3(d) we show the cross-sectional FESEM image of the SiO 2 thin film deposited at the back side of the substrate holder, where the growth takes place under very weak or no plasma ion impingement. 16 This assumption is supported by the experimental observation that no plasma glow develops at the back side of the substrate holder during the deposition. Although Si atoms directionality, and therefore the surface shadowing mechanism, is expected to be very different in this configuration, Fig.…”

“…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.…”

“…7-9). Some relevant scientific issues regarding the influence of the plasma on the film growth are linked to (i) cathode poisoning and process instability, 10,11 (ii) changes in the momentum and kinetic energy of the sputtered particles when arriving at the film due to scattering processes on plasma particles, [12][13][14][15][16] and (iii) positive and negative ion impingement on the film surface during growth. [17][18][19][20][21] Cathode poisoning is an undesired effect that takes place when there is an excess of reactive gas in the deposition reactor.…”

Supported plasma-made 1D heterostructures: perspectives and applications

“…The formation of homogeneous thin film microstructures by PECVD has been associated with a growing mechanism where surface diffusion of ad-species is the controlling process [55][56][57], while the columnar growth has been related with the existence of shadowing effects and a high sticking coefficient of the ad-species coming from the plasma [55,56,60]. In connection with this columnar growth of thin films, it has been realized that in PECVD processes the particles arrive with a wide distribution of incoming angles and that the actual angular distribution is a key factor in determining the microstructure developed by the films [58,59]. Figure 1 shows as an example two cross-section scanning electron microscope (SEM) micrographs obtained for columnar amorphous TiO 2 ( Fig.…”

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.…”