Transmission electron microscopy study of n= 1–5 Srn+1TinO3n+1 epitaxial thin films

2001 ◽  
Vol 16 (7) ◽  
pp. 2013-2026 ◽  
Author(s):  
W. Tian ◽  
X. Q. Pan ◽  
J. H. Haeni ◽  
D. G. Schlom

Epitaxial Srn+1TinO3n+1 thin films with n = 1–5 were synthesized on (001) SrTiO3 substrates by reactive molecular beam epitaxy. The structure and microstructure of the films were investigated by x-ray diffraction, transmission electron microbeam diffraction, and high-resolution transmission electron microscopy (HRTEM) in combination with computer image simulations. Both diffraction and HRTEM studies revealed that all the films are epitaxially oriented with their c axis perpendicular to the (001) SrTiO3 plane of the substrate. Detailed investigations using quantitative HRTEM methods indicated that the films have the expected n = 1–5 structures of the Ruddlesden–Popper Srn+1TinO3n+1 homologous series. Among these films, Sr2TiO4, Sr3Ti2O7, and Sr4Ti3O10 thin films are nearly free of intergrowths, while Sr5Ti4O13 and Sr6Ti5O16 thin films contain noticeably more antiphase boundaries in their perovskite sheets and intergrowth defects. We show that these results are consistent with what is known about the thermodynamics of Srn+1TinO3n+1 phases.

2001 ◽  
Vol 7 (S2) ◽  
pp. 558-559
Author(s):  
K.M. Jones ◽  
Y. Yan ◽  
F.S. Hasoon ◽  
M.M. Al-Jassim

Polycrystalline CdTe is a promising candidate for solar cells due to its nearly ideal band-gap, high absorption coefficient, and ease of film fabrication. Small-area CdTe/CdS cells with efficiencies of 16.0% have been demonstrated. The structure of a typical CdTe/CdS solar cell (Figure 1) consists of a glass superstrate, on which a thin layer of SnO2 is deposited (front contact), n-type CdS, p-type CdTe, and a back contact. Prior to applying the back contact to the CdTe, etching of the CdTe surface using a mixture of nitric and phosphoric (NP) acids is normally needed. It is known that the etching depletes a crystalline CdTe surface of Cd and creates a Te-rich layer. Two effects of the Te-rich layer has been proposed, namely, forming a Te-CdTe low-series-resistance contact and improving CdTe device stability by the gettering of Cu. Thus, the NP etching is an important process in the CdTe device fabrication. in this paper, we report on transmission electron microscopy (TEM) study of the microstructure of the surface of NP etched CdTe thin films.


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