Model predictive control of film porosity in thin film deposition

Hu, Gangshi; Orkoulas, Gerassimos; Christofides, Panagiotis D.

doi:10.1109/acc.2009.5160202

Cited by 2 publications

(2 citation statements)

References 23 publications

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“…Numerous groups have modelled deposition processes of thin films [8][9][10][11][12], but here we look specifically at ZnO. In this paper we investigate, at the atomistic level, the effect of using different deposition processes on the growth of ZnO.…”

Section: Introductionmentioning

confidence: 99%

Modelling the growth of ZnO thin films by PVD methods and the effects of post-annealing

Blackwell

Smith

Kenny

et al. 2013

J. Phys.: Condens. Matter

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Results are presented for modelling of the evaporation and magnetron sputter deposition of Zn x O y onto an O-terminated ZnO (000 1) wurtzite surface. Growth was simulated through a combination of molecular dynamics (MD) and an on-the-fly kinetic Monte Carlo (otf-KMC) method, which finds diffusion pathways and barriers without prior knowledge of transitions. We examine the effects of varying experimental parameters, such as substrate bias, distribution of the deposition species and annealing temperature. It was found when comparing evaporation and sputtering growth that the latter process results in a denser and more crystalline structure, due to the higher deposition energy of the arriving species. The evaporation growth also exhibits more stacking faults than the sputtered growth. Post-annealing at 770 K did not allow complete recrystallization, resulting in films which still had stacking faults where monolayers formed in the zinc blende phase, whereas annealing at 920 K enabled the complete recrystallization of some films to the wurtzite structure. At the latter temperature atoms could also sometimes be locked in the zinc blende phase after annealing. When full recrystallization did not take place, both wurtzite and zinc blende phases were seen in the same layer, resulting in a phase boundary. Investigation of the various distributions of deposition species showed that, during evaporation, the best quality film resulted from a stoichiometric distribution where only ZnO clusters were deposited. During sputtering, however, the best quality film resulted from a slightly O rich distribution. Two stoichiometric distributions, one involving mainly ZnO clusters and the other involving mainly single species, showed that the distribution of deposition species makes a huge impact on the grown film. The deposition of predominantly single species causes many more O atoms at the surface to be sputtered or reflected, resulting in an O deficiency of up to 18% in the deposited film and therefore resulting in more stacking faults and phase boundaries. The methods used allow analysis of key mechanisms that occur during the growth process and give hints as to the optimum conditions under which complete crystalline layers can form.

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Section: Introductionmentioning

confidence: 99%

Modelling the growth of ZnO thin films by PVD methods and the effects of post-annealing

Blackwell

Smith

Kenny

et al. 2013

J. Phys.: Condens. Matter

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“…Previously, researchers have modelled thin film growth and specifically modelled the different deposition processes used in the growth of numerous different materials [14][15][16][17] . Theoretical and experimental work has been carried out in the past on the thin film behaviour of Ag and Al.…”

Section: Introductionmentioning

confidence: 99%

Modeling evaporation, ion-beam assist, and magnetron sputtering of thin metal films over realistic time scales

et al. 2012

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A long time scale dynamics technique has been used to model the evaporation, ion-beam assist and magnetron sputtering of thin metal films over realistic time scales. Two fcc metals have been investigated; silver and aluminium. We illustrate how the technique can be used to model growth of these films over experimental time scales, while investigating individual growth mechanisms and surface diffusion events. Long time dynamics is achieved through an on-the-fly Kinetic Monte Carlo method, which determines diffusion pathways and barriers, in parallel, with no prior knowledge of the involved transitions. It was found that Ag has the ability to grow smooth surfaces, using several mechanisms including multiple atom concerted motion, exchange mechanisms and damage and repair systems. Ag {111} and {100} grew dense, complete and crystalline film when sputtering was simulated, whereas evaporation produced incomplete layers. The inclusion of Ar in the ionbeam assisted evaporation of Ag {111} aided growth by transferring more energy to the surface atoms allowing increased diffusion. Al {111} however shows slightly different patterns; growth via evaporation and magnetron sputtering shows only slight differences and the inclusion of the ionbeam assist actually damages the film beyond repair producing subsurface Ar clusters where Al atoms were displaced creating voids throughout the film. Al {100}, similar to Ag {100} grows denser and more complete film when grown via sputtering rather than evaporation. Results show that the energy of the deposition method used, plays a vital role in the resulting thin film and substrate quality.

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Model predictive control of film porosity in thin film deposition

Cited by 2 publications

References 23 publications

Modelling the growth of ZnO thin films by PVD methods and the effects of post-annealing

Modelling the growth of ZnO thin films by PVD methods and the effects of post-annealing

Modeling evaporation, ion-beam assist, and magnetron sputtering of thin metal films over realistic time scales

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