R.f. planar magnetron sputtered ZnO films I: Structural properties

Pol, F.C.M. van de; Blom, F.C.; Popma, T.J.A.

doi:10.1016/0040-6090(91)90074-8

Cited by 127 publications

(53 citation statements)

References 14 publications

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“…For initially smooth sputter-deposited ZnO:Al films a surface texture is realized by postdeposition wet-chemical etching. 29, 30 Kluth et al related the influence of pressure and substrate temperature during radio frequency ͑rf͒ sputter deposition of ZnO:Al at a fixed alumina content of 2 wt % in the sputter target to structural properties and postetching surface topography in a modified Thornton model. 30 They showed that, depending on sputter parameters, craterlike surface topography with typical lateral length scales of 1 -2 m and depths of about 200-400 nm develops in a self-organized fashion.…”

Section: Introductionmentioning

confidence: 99%

The effect of front ZnO:Al surface texture and optical transparency on efficient light trapping in silicon thin-film solar cells

Berginski

Hüpkes

Schulte

et al. 2007

Journal of Applied Physics

489

275

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This study addresses the material properties of magnetron-sputtered aluminum-doped zinc oxide (ZnO:Al) films and their application as front contacts in silicon thin-film solar cells. Optimized films exhibit high conductivity and transparency, as well as a surface topography with adapted light-scattering properties to induce efficient light trapping in silicon thin-film solar cells. We investigated the influence on the ZnO:Al properties of the amount of alumina in the target as well as the substrate temperature during sputter deposition. The alumina content in the target influences the carrier concentration leading to different conductivity and free carrier absorption in the near infrared. Additionally, a distinct influence on the film growth of the ZnO:Al layer was found. The latter affects the surface topography which develops during wet-chemical etching in diluted hydrochloric acid. Depending on alumina content in the target and heater temperature, three different regimes of etching behavior have been identified. Low amounts of target doping and low heater temperatures result in small and irregular features in the postetching surface topography, which does not scatter the light efficiently. At higher substrate temperatures and target doping levels, more regularly distributed craters evolve with mean opening angles between 120° and 135° and lateral sizes of 1–3μm. These layers are very effective in light scattering. In the third regime—at very high substrate temperatures and high doping levels—the postetching surface is rather flat and almost no light scattering is observed. We applied the ZnO:Al films as front contacts in thin-film silicon solar cells to study their light-trapping ability. While high transparency is a prerequisite, light trapping was improved by using front contacts with a surface topography consisting of relatively uniformly dispersed craters. We have identified a low amount of target doping (0.5–1wt%) and relatively high substrate temperatures (about 350–450°C as sputter parameters enabling short-circuit current densities as high as 26.8mA∕cm2 in μc-Si:H pin cells with an i-layer thickness of 1.9μm. Limitations on further improvements of light-trapping ability are discussed in comparison with the theoretical limitations and Monte Carlo simulations presented in the literature.

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Section: Introductionmentioning

confidence: 99%

The effect of front ZnO:Al surface texture and optical transparency on efficient light trapping in silicon thin-film solar cells

Berginski

Hüpkes

Schulte

et al. 2007

Journal of Applied Physics

489

275

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“…Magnetron sputtering deposits thin films of ZnO using RF, DC or pulsed DC power [5,6]. Targets can be metal Zn (DC) or ZnO (RF and pulsed DC).…”

Section: Introductionmentioning

confidence: 99%

“…Metal-oxide thin films can be deposited using a variety of industrial-scale processes, including evaporation (thermal and electron beam) and reactive magnetron sputtering [3][4][5][6]. The evaporation process involves evaporation of Zn x O y molecules onto the substrate with kinetic energy typically <1 eV.…”

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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“…The occurrence of these columnar microstructures has been confirmed by several studies that have employed scanning electron microscopy (SEM). [16][17][18][19] X-ray diffraction (XRD) has been used to determine that the columnar grains tend to exhibit a preferred orientation with the plane of a planar substrate. The standard deviation of the x-ray diffraction rocking curve of the 0002 diffraction peak (s0002) is commonly used to characterize the degree of [0001] texture, which is dependent on deposition conditions and the substrate material.…”

Section: Introductionmentioning

confidence: 99%

Planar defects in ZnO thin films deposited on optical fibers and flat substrates

Sagalowicz

Fox

1999

J. Mater. Res.

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The microstructure and the defects of ZnO coatings deposited at room temperature by sputtering onto fibers and flat substrates were characterized using transmission electron microscopy (TEM), scanning electron microscopy, and x-ray diffraction (XRD). XRD shows that the films have a [0001] preferred orientation and a large angular width of the 0002 reflection. According to TEM observations, the film microstructure consists of columnar grains which contain large concentrations of basal planar defects and dislocations. High-resolution transmission electron microscopy analysis and the associated image simulation are in full agreement with the presence of single (type I) and double (type II) stacking faults. The relation between the observed defects and the 0002 peak broadening is discussed.

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R.f. planar magnetron sputtered ZnO films I: Structural properties

Cited by 127 publications

References 14 publications

The effect of front ZnO:Al surface texture and optical transparency on efficient light trapping in silicon thin-film solar cells

The effect of front ZnO:Al surface texture and optical transparency on efficient light trapping in silicon thin-film solar cells

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

Planar defects in ZnO thin films deposited on optical fibers and flat substrates

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