Multilayer Transparent Conducting Oxide Thin Film Produced by Linear Combinatorial Synthesis
- PDF / 533,334 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 36 Downloads / 191 Views
JJ2.4.1
Multilayer Transparent Conducting Oxide Thin Film Produced by Linear Combinatorial Synthesis Xiaonan Li National Renewable Energy Laboratory 1617 Cole Boulevard, Golden, CO 80401, U.S.A, ABSTRACT Multilayer transparent conducting oxide (TCO) structures consisting of alternating layers of tin oxide (SnO2) and cadmium oxide (CdO) pairs was studied. A low-pressure metalorganic chemical vapor deposition with a linear combinatorial approach was used to fabricate the libraries. Three libraries were studied with the pair thickness range covered from 500 nm to 4 nm. For pairs thicker than 150 nm, the material properties of the multilayer simply show a combination of CdO and SnO2 characteristics. When pair thinner than 70 nm, the interface effect started emerging. As pairs became thinner than 20 nm, the new compound phase was formed. INTRODUCTION Among the various TCO materials, CdO and SnO2 are two important compounds that having relatively different properties. CdO has demonstrated extremely high electron mobility that is 510 times higher than the most widely used TCOs, but has a relative narrow optical bandgap of 2.28 eV [1]. SnO2 has a wide optical bandgap of 3.6 eV, but its electron mobility is only about 20~50 cm2/V-s. Combining these two compounds should take advantage of their favorable characteristics. For example, one study indicated that Cd-containing compounds might have an advantage for reaching high electron mobility because of the 5s orbital of the Cd cations [2]. Cadmium stannate (Cd2SnO4) is a good example of a combination of these two compounds [3,4]. Our previous work indicated that by simultaneously flowing tetramethyltin (TMT) and dimethylcadmium (DMCd) into the reaction chamber, a high electron mobility Cd-Sn-O compounds could be formed in a wide composition region [5]. The purpose of this investigation is to determine whether a multilayer structure consisting of alternating layer pairs of SnO2 and CdO would yield a Cd-Sn-O compound with favorable optical and electrical properties. Three libraries with different pair thicknesses and numbers of pairs are analyzed in this study. The first library consisted of a bilayer (one pair) of SnO2-CdO structures with a maximum total thickness of 0.50 µm. The second and third libraries contained multilayers (10 and 60 pairs) of SnO2-CdO structures with a maximum total thickness of 0.7 µm and 1.18 µm, respectively. Properties for each library are discussed in the following section. EXPERIMENTS The three multilayer SnO2-CdO libraries studied were created using a low-pressure metalorganic chemical vapor deposition (LPMOCVD) system. The individual layer thicknesses were varied in two different ways to study the mixed-phase properties: first, by reducing both CdO and SnO2 layer thicknesses simultaneously; second, by changing the CdO/SnO2 ratio along
JJ2.4.2
the x-axis. With the combinatorial approach, a wide range of individual layer thicknesses and combinations consisting of CdO and SnO2 were formed in only a few deposition runs. TMT and DMCd were used as Sn
Data Loading...
