A comparative study of electronic and structural properties of polycrystalline and epitaxial magnetron-sputtered ZnO:Al and Zn1-xMgxO:Al Films—Origin of the grain barrier traps

Bikowski, André; Ellmer, K.

doi:10.1063/1.4817376

Cited by 37 publications

(27 citation statements)

References 52 publications

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“…This again is an indication that additional effects influence the electrical transport in ZnO films directly at the interface. As already shown earlier for ZnO:Al films, 33 we confirmed that the electrical film properties are quite insensitive to the crystallographic film structure, i.e., to preferred orientation, grain size and even polycrystalline or epitaxial growth. This means, after the coalescence of the nucleating islands the resistivity of the films is almost constant.…”

Section: Electrical Properties Of Azo and Ito Filmssupporting

confidence: 86%

Microstructure evolution of Al-doped zinc oxide and Sn-doped indium oxide deposited by radio-frequency magnetron sputtering: A comparison

Nie

Bikowski

Ellmer

2015

Journal of Applied Physics

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Section: Electrical Properties Of Azo and Ito Filmssupporting

confidence: 86%

Microstructure evolution of Al-doped zinc oxide and Sn-doped indium oxide deposited by radio-frequency magnetron sputtering: A comparison

Nie

Bikowski

Ellmer

2015

Journal of Applied Physics

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“…7). In particular, the lowest FWHM rc (i.e., $2.6 found for jV d j ¼ 56 V sample) compared well with the best value of magnetron sputtered polycrystalline AZO films (2.5 , RF deposition at 250 C), 30,31 indicating high crystallinity of our films. 8.…”

Section: Structural Characterizationsupporting

confidence: 68%

“…Two types of FWHM values were obtained: one from the conventional h-2h scans (FWHM 2h ) and the other from the rocking curve scans (FWHM rc ). 30,32 Actually, for a high density of carriers (>10 20 cm À3 ) in polycrystalline degenerate semiconductors, their mobility is dominated by ionized impurity scattering, not by grain boundary scattering. 10), with the lowest values found in the optimal jV d j window.…”

Section: Structural Characterizationmentioning

confidence: 99%

Optimizing the discharge voltage in magnetron sputter deposition of high quality Al-doped ZnO thin films

Meng

Peng²,

Xu³

et al. 2015

Journal of Vacuum Science &Amp; Technology A: Vacuum, Surfaces, and Films

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Articles you may be interested inCarrier mobility of highly transparent conductive Al-doped ZnO polycrystalline films deposited by radio-frequency, direct-current, and radio-frequency-superimposed direct-current magnetron sputtering: Grain boundary effect and scattering in the grain bulk J. Appl. Phys. 117, 045304 (2015); 10.1063/1.4906353Correlations between 1/f noise and thermal treatment of Al-doped ZnO thin films deposited by direct current sputtering Transparent conducting Si-codoped Al-doped ZnO thin films prepared by magnetron sputtering using Al-doped ZnO powder targets containing SiC Transparent conducting Al-doped ZnO thin films prepared by magnetron sputtering with dc and rf powers applied in combination Investigation on the electrical properties and inhomogeneous distribution of ZnO:Al thin films prepared by dc magnetron sputtering at low deposition temperatureThe role of negative ions in the sputter deposition of oxides can be termed negative in the sense that they typically cause radiation-induced structural damage during film growth. For magnetron sputtered Al-doped ZnO (AZO) films, efforts have been made to alleviate the radiation damage by decreasing the discharge voltage jV d j, with $100 V being the lower limit explored. Here, the authors report initial results of depositing highly conductive and transparent AZO films by reducing jV d j down to 40 V. The deposition was performed by sputtering an AZO target using dense magnetron discharges, in which an 81 MHz radio frequency power was superimposed onto a DC power applied to the cathode. The authors found an optimal jV d j window within which high quality AZO films, with a <4 Â 10 À4 X cm resistivity, >30 cm 2 /(V s) Hall mobility, and >88% visible transmittance, were obtained at relatively high deposition rates (>30 nm/min). Based on the corresponding structural features, i.e., a full mass density coupled with a slight c-axis contraction along the out-of-plane direction, energetic negative ions were identified to have dominated in the structural evolution. The jV d j window was then interpreted in terms of two competitive kinetic processes simultaneously caused by the energetic negative ions: void reduction via ballistic relocation of atoms as well as residual radiation-induced damage. The findings thus reveal a positive role (i.e., concomitant densification) played by the negative ions in growing high quality fully dense AZO films, which has been overshadowed by the excessive radiation damage induced by ions with relatively higher energies.

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“…Instead of q opt , most authors compute the mobility l opt . [29][30][31][32][33][34][35][36][37][38][39][40] The determination of l opt by modeling of optical spectra requires the effective mass m*, whereas the resistivity q opt can be evaluated without knowing m*. As the effective mass is prone to considerable uncertainties, 30,35,36,40 we will focus on the resistivity q opt .…”

Section: Methodsmentioning

confidence: 99%

Role of the dopant aluminum for the growth of sputtered ZnO:Al investigated by means of a seed layer concept

Sommer

Stanley

Köhler

et al. 2015

Journal of Applied Physics

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This work elucidates the effect of the dopant aluminum on the growth of magnetron-sputtered aluminum-doped zinc oxide (ZnO:Al) films by means of a seed layer concept. Thin (<100 nm), highly doped seed layers and subsequently grown thick (∼800 nm), lowly doped bulk films were deposited using a ZnO:Al2O3 target with 2 wt. % and 1 wt. % Al2O3, respectively. We investigated the effect of bulk and seed layer deposition temperature as well as seed layer thickness on electrical, optical, and structural properties of ZnO:Al films. A reduction of deposition temperature by 100 °C was achieved without deteriorating conductivity, transparency, and etching morphology which renders these low-temperature films applicable as light-scattering front contact for thin-film silicon solar cells. Lowly doped bulk layers on highly doped seed layers showed smaller grains and lower surface roughness than their counterpart without seed layer. We attributed this observation to the beneficial role of the dopant aluminum that induces an enhanced surface diffusion length via a surfactant effect. The enhanced surface diffusion length promotes 2D-growth of the highly doped seed layer, which is then adopted by the subsequently grown and lowly doped bulk layer. Furthermore, we explained the seed layer induced increase of tensile stress on the basis of the grain boundary relaxation model. The model relates the grain size reduction to the tensile stress increase within the ZnO:Al films. Finally, temperature-dependent conductivity measurements, optical fits, and etching characteristics revealed that seed layers reduced grain boundary scattering. Thus, seed layers induced optimized grain boundary morphology with the result of a higher charge carrier mobility and more suitable etching characteristics. It is particularly compelling that we observed smaller grains to correlate with an enhanced charge carrier mobility. A seed layer thickness of 5 nm was sufficient to induce the beneficial effects.

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A comparative study of electronic and structural properties of polycrystalline and epitaxial magnetron-sputtered ZnO:Al and Zn1-xMgxO:Al Films—Origin of the grain barrier traps

Cited by 37 publications

References 52 publications

Microstructure evolution of Al-doped zinc oxide and Sn-doped indium oxide deposited by radio-frequency magnetron sputtering: A comparison

Microstructure evolution of Al-doped zinc oxide and Sn-doped indium oxide deposited by radio-frequency magnetron sputtering: A comparison

Optimizing the discharge voltage in magnetron sputter deposition of high quality Al-doped ZnO thin films

Role of the dopant aluminum for the growth of sputtered ZnO:Al investigated by means of a seed layer concept

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