Growth of CdTe Films on Amorphous Substrates Using CaF2 Nanorods as a Buffer Layer

Abstract

Continuous biaxially textured CdTe films were grown on biaxial CaF 2 buffer layers. The CaF 2 nanorods were grown by oblique angle vapor deposition and possessed a {111}h121i biaxial texture. The CdTe film was deposited by metal organic chemical vapor deposition (MOCVD). Film morphology and the CdTe/ CaF 2 interface were studied by scanning electron microscopy and transmission electron microscopy. Characterization showed that small CdTe grains formed initially from the CaF 2 surfaces. These small grains then merged into large columnar grains during growth. Analysis revealed that the crystalline orientation of the CdTe film followed the biaxial texture of the CaF 2 nanorods.

RHEED Pole Figure Measurements of Biaxial Thin Film Growth Front Evolution

“…Our previous work shows that CaF 2 nanorods grown by the oblique angle vapor deposition on amorphous substrates exhibit a biaxial texture [35,36]. This CaF 2 can be used as a buffer layer to grow biaxial thin films for various applications [6,7,9,10]. In Fig.…”

“…All these films were deposited using the oblique angle deposition (or inclined-substrate deposition) technique [37][38][39][40][41][42][43]. We have also applied the technique to measure the CdTe biaxial films grown on biaxial CaF 2 nanostructures deposited using the oblique angle deposition technique [9,10]. Oblique-angle deposition has been used to grow magnetic films with magnetic anisotropy [44], high reflectance mirrors for optics [37], and various nanostructures [38, 39, 41-43, 45, 46].…”

“…A recent example is the growth of biaxially textured films as buffer layers for subsequent growth of highly oriented (both out-of-plane and in-plane) high T c superconducting films to achieve high current density [5]. It has also been suggested that this approach can be extended to include the growth of biaxial semiconductor films on biaxially textured buffer layers on glass [6][7][8], amorphous substrates [9,10] and metal sheets [11,12] for efficient and inexpensive solar cell applications. Other potential applications include solid state lighting and optoelectronic devices.…”

Quasi-single Crystal Semiconductors on Glass Substrates Through Biaxially Oriented Buffer Layers

“…Small angle grain boundary semiconductor films on non-single crystal substrate can be achieved by first creating a biaxial buffer layer followed by depositing the semiconductor film [10][11][12][13][14][15][16]. Biaxial buffer layers can be grown on non-single crystal substrates such as glass by a number of techniques including ion assisted deposition [10][11][12] and oblique angle deposition [13][14][15][16]. A biaxial film is not exactly a single crystal, but it has both preferred out-ofplane and in-plane orientations with small angle grain boundaries.…”

“…An alternative and scalable method to produce biaxial buffer layers is the oblique angle deposition (or the inclined substrate deposition) technique where growth on large area can be achieved. The oblique angle deposition technique has been used to produce buffer layers such as MgO [18,19], as well as CeO 2 [12,13] and CaF 2 [14][15][16] to grow biaxial semiconductors. From the material point of view, CaF 2 buffer layers grown under normal incident vapor on single crystal Si substrates have been used extensively for the growth of single crystal semiconductor films such as CdTe and GaAs [20][21][22].…”