Matthias Rottmann

Photoelectrochemical properties of n-GaAs/ITO electrodes produced by d.c. sputtering

Abstract Coating of n-GaAs with transparent conductive films, such as ITO (indium tin oxide), should protect this material against photodecomposition. n-GaAs/ITO samples were produced by reactive dc sputtering using pure oxygen as the reactive sputtering gas. The electrochemical and photoelectrochemical properties of these devices were investigated in different aqueous electrolytes. The cyclic voltammograms of n-GaAs/TTO devices show increasing photocurrent with increasing scan number. This general behaviour can be explained by a corrosion of the ITO film as well as of the n-GaAs substrate. Thus, the produced samples show only low time stability for use as photoelectrodes. An explanation for this behaviour is given.

Change of optical, electrical, and structural properties of sputtered indium tin oxide films by application of a new reactive sputter atmosphere

Highly qualitative indium tin oxide (ITO) films were deposited by reactive dc-sputter technique on glass and quartz substrates. Both pure H2O vapor and pure O2 have been used as reactive sputtering atmosphere. The optical constants refractive index and absorption coefficient were calculated from reflection and transmission spectra in the infrared (IR) region. Using the Drude theory the electrical parameters free carrier concentration and carrier mobility of the ITO-films were contactless determined from IR reflection spectra. The dc-H2O-sputtered ITO-films show improved optical and electrical properties. For application as transparent window material they distinguish by high visual (VIS) transmittance and high IR- reflectance. Moreover these ITO-films show a high free carrier concentration of N equals 6 X 1020 cm-3 directly after deposition compared with N equals 4 X 1020 cm-3 for dc-O2-sputtered ITO-films after thermal annealing. The differences between optical and electrical properties of de-O2- and dc-H2O-sputtered ITO-films are discussed in regard to their crystal structure and surface morphology.

FTIR spectrometric investigation of tin-doped indium oxide coatings on quartz glasses

FTIR spectra of tin-doped indium oxide (ITO) coatings on quartz substrates are interpreted by fitting model functions. ITO coatings are prepared by dc sputtering. The sputter gases contain O2, Ar, and CF4, CCl2F2 and CBr2F2, respectively. The measured thickness d of deposited ITO coatings on quartz glass substrates differs between 40 and 540 nm. Carrier concentration and mobility are estimated.