Indium-cadmium-oxide films having exceptional electrical conductivity and optical transparency: Clues for optimizing transparent conductors

Abstract

Materials with high electrical conductivity and optical transparency are needed for future flat panel display, solar energy, and other opto-electronic technologies. In xCd1-xO films having a simple cubic microstructure have been grown on amorphous glass substrates by a straightforward chemical vapor deposition process. The x ‫؍‬ 0.05 film conductivity of 17,000 S͞cm, carrier mobility of 70 cm 2 ͞Vs, and visible region optical transparency window considerably exceed the corresponding parameters for commercial indium-tin oxide. Ab initio electronic structure calculations reveal small conduction electron effective masses, a dramatic shift of the CdO band gap with doping, and a conduction band hybridization gap caused by extensive Cd 5s ؉ In 5s mixing.

Electronic structure of crystalline binary and ternaryCd−Te−Ocompounds

“…Previous band diagram calculations 22,25,26,27,28,29,69,71,72 and the present one provide different interpretations for ordering of the indirect bandgaps.…”

Transparent and conductive indium doped cadmium oxide thin films prepared by pulsed filtered cathodic arc deposition

“…Table 2 shows the electrical properties of the pulsed arc-grown ICO films compared to values reported for several other growth techniques. Except for the optimized PLD-grown films [19], the electrical properties of films prepared by PFCAD in this study are typically better than those of ICO films prepared by other techniques on glass or even on single crystalline MgO substrates [10,12,14,30,[33][34][35][36]. Though the as-deposited films in this study show a little higher resistivity than that of the optimized PLD-grown films, comparable mobility with a higher near infrared transmittance and a much wider transparent range are observed, which is of special interest to multi-junction solar cells.…”

“…It is known that the optical absorption edge can be considerably widened via a Burstein-Moss shift by increasing the electron concentration [8,9]. Therefore, various dopants, including indium (In), tin (Sn), titanium (Ti), zinc (Zn), aluminum (Al), and fluorine (F), have been introduced into CdO to simultaneously increase the conductivity and widen the bandgap [10][11][12][13][14][15][16][17][18]. Among these doping elements, indium has been investigated in CdO since the two elements have very close ionic radii and both show excellent photoelectric properties [15,19].…”

“…Among these doping elements, indium has been investigated in CdO since the two elements have very close ionic radii and both show excellent photoelectric properties [15,19]. Furthermore, In-doping can favorably alter the CdO band structure by extensive mixing of In 5s and Cd 5s states, which lowers optical absorption by weakening the intraband transitions [12]. Doped and undoped CdO thin films have been prepared on various substrates by different film growth techniques.…”

Structural, optical, and electrical properties of indium-doped cadmium oxide films prepared by pulsed filtered cathodic arc deposition

“…Fortunately, the bandgap of CdO can be considerably widened via the Burstein-Moss shift by increasing the electron concentration [4][5][6]. Therefore, dopants including indium (In), tin (Sn), titanium (Ti), zinc (Zn), aluminum (Al), yttrium (Y), and fluorine (F) have been introduced into CdO in order to improve the conductivity and widen the bandgap [4,[6][7][8][9][10][11][12]. Aside from environmental issues, doped CdO materials are nearly ideal for photoelectrical and other possible applications, such as solar energy harvesting, optical communications, gas sensors, thin-film resistors, IR heat mirrors, etc.…”