MOCVD Growth of Transparent Conducting Cd₂SnO₄ Thin Films

Abstract

Transparent conducting oxides (TCOs) are an important component of a great many opto-electronic device structures, including flat panel displays, organic light-emitting diodes (OLEDs), and photovoltaics (PVs).[1] Tin-doped indium oxide (ITO) is the best known and most studied of these materials, [2,3] but has severe limitations. The high price of indium, sub-optimal conductivity and transparency window, and chemical/interfacial instability in many PV [4] and OLED [5] structures, have stimulated a search for alternative materials. Cd 2 SnO 4 has been the subject of intense investigation, [6±11] exploring its potential as a low-cost, high-performance alternative to ITO, and Cd 2 SnO 4 has been incorporated into PV device structures with promising results (efficiencies > 15 %). [12,13] Cd 2 SnO 4 thin films have been prepared by several different growth techniques including radio frequency (RF) magnetron sputtering, [9,10,13±16] RF reactive sputtering, [6] pulsed laser deposition (PLD), [17] dip coating, [8,18] and sol±gel methods. [19] As-deposited films produced by these techniques are often amorphous and require high temperature annealing to promote crystallization and to enhance optoelectronic properties. We are, however Its attractive characteristics include a straightforward, onestep aqueous synthesis under ambient conditions from commercially available starting materials, excellent volatility, as well as excellent air and thermal stability. Further advances in cadmium precursor technology by our laboratory, [24] and the complementary approaches of other groups, [25] have resulted in an increased film growth capability for discovery, synthesis, and optimization of cadmium-containing opto-electronic materials. In this contribution, we report the first growth of transparent conducting Cd 2 SnO 4 films by a MOCVD process. As-deposited, the films are highly crystalline on glass substrates at the relatively low growth temperature of 365 C, and have electrical and optical properties rivaling those of commercial ITO. CdO-SnO 2 films were grown on Corning 1737F glass (softening point = 975 C) at 365 C, and carrier gas ratios were adjusted until films with 2:1 Cd/Sn ratios (± 1 %) were obtained, as determined by inductively coupled plasma atomic-emission spectroscopy (ICP-AES). Films grown for 1.5 h have a thickness of 970 nm by profilometry (growth rate = 10.8 nm min ±1 ). The as-deposited films are highly crystalline with the cubic spinel Cd 2 SnO 4 crystal structure, [26] as determined by X-ray diffraction (XRD) h±2h scans ( Fig. 1). A small amount of CdO may be responsible for the broad (400) reflection at 39. Scanning electron miCommunications

Spray-pyrolysis Cd2SnO4 films for electrochemical applications

“…Films with near stoichiometric composition exhibit the specific resistivity of about 2 mΩcm. This value is higher than the achieved value for films grown by CVD (∼ 0.5 mΩcm [16]), but it is comparable to the values reported by other authors (1-4 mΩcm). [9,10,12,13,15,17].…”

“…Various deposition techniques were applied for the growth of Cd 2 SnO 4 thin films: rf-sputtering [8][9][10][11], dc-sputtering [12], dip-coating [13][14][15], sol-gel [6,7], and chemical vapour deposition (CVD) [16,17]. The optical, electrical and electrochemical properties of Cd 2 SnO 4 films are sensitive to deposition method and conditions.…”

Tin(II) aminoalkoxides and heterobimetallic derivatives: the structures of Sn6(O)4(dmae)4, Sn6(O)4(OEt)4 and [Sn(dmae)2Cd(acac)2]2

“…Previous methods for producing these materials include vacuum evaporation, 57 co-precipitation 55,59 and r.f. sputtering, 60 and one report on a dip-coating procedure employed mixtures of Sn(OR) 4 66 We have thus employed a β-diketonate derivative as the source of the cadmium. Addition of an equimolar quantity of 1 to a suspension of [Cd(acac) 2 ] m in toluene followed by heating to ca 60…”

Investigation of hexadecanethiol self-assembled monolayers on cadmium tin oxide thin films

“…It combines the beneficial characteristics of SnO 2 and CdO in that it has low emissivity coupled to high electron mobility [20]. In fact, the conductivity and bandgap obtained by metal-organic chemical vapor deposition [23] is comparable to commercially available ITO and can be improved upon by changing the deposition precursor [23,24].…”