Grain growth, anomalous scaling, and grain boundary grooving in polycrystalline CdTe thin films (original) (raw)
Related papers
Anomalous scaling and super-roughness in the growth of CdTe polycrystalline films
Physical Review B, 2008
CdTe films grown on glass substrates covered by fluorine doped tin oxide by Hot Wall Epitaxy (HWE) were studied through the interface dynamical scaling theory. Direct measures of the dynamical exponent revealed an intrinsically anomalous scaling characterized by a global roughness exponent alpha\alphaalpha distinct from the local one (the Hurst exponent HHH), previously reported [Ferreira \textit{et al}., Appl. Phys. Lett. \textbf{88}, 244103 (2006)]. A variety of scaling behaviors was obtained with varying substrate temperature. In particular, a transition from a intrinsically anomalous scaling regime with Hnealpha<1H\ne\alpha<1Hnealpha<1 at low temperatures to a super-rough regime with Hnealpha>1H\ne\alpha>1Hnealpha>1 at high temperatures was observed. The temperature is a growth parameter that controls both the interface roughness and dynamical scaling exponents. Nonlocal effects are pointed as the factors ruling the anomalous scaling behavior.
Journal of Physics: Energy, 2021
Many technologies deposit thin films on inexpensive substrates, resulting in small grains due to classic nucleation and grain growth theory. For example, state-of-the-art solar cells are made by depositing CdSeTe and CdTe layers on inexpensive glass coated with nanocrystalline transparent conducting oxides (TCOs), like SnO2. Characteristically, the grain size of these films is on the order of the film thickness, i.e. a few microns. CdTe small-grain films have poor electro-optical properties and require CdCl2 passivation which fails to fully passivate grain boundaries, causes carrier compensation, and prevents implementing other II–VI alloys and materials to improve performance. Here, we present a method to increase grain size to 1 mm in CdSexTe1−x thin films deposited on glass/TCO substrates without CdCl2 treatment. The colossal grain growth is driven by mechanisms distinct from classic nucleation, grain growth, and Ostwald ripening and only occurs at low selenium content (x ∼ 0.1)....
Microscopy and microanalysis : the official journal of Microscopy Society of America, Microbeam Analysis Society, Microscopical Society of Canada, 2015
The performance of polycrystalline CdTe photovoltaic thin films is expected to depend on the grain boundary density and corresponding grain size of the film microstructure. However, the electrical performance of grain boundaries within these films is not well understood, and can be beneficial, harmful, or neutral in terms of film performance. Electron backscatter diffraction has been used to characterize the grain size, grain boundary structure, and crystallographic texture of sputtered CdTe at varying deposition pressures before and after CdCl2 treatment in order to correlate performance with microstructure. Weak fiber textures were observed in the as-deposited films, with (111) textures present at lower deposition pressures and (110) textures observed at higher deposition pressures. The CdCl2-treated samples exhibited significant grain recrystallization with a high fraction of twin boundaries. Good correlation of solar cell efficiency was observed with twin-corrected grain size wh...