THIN-FILM DEPOSITION OF CONDUCTIVE TIN OXIDE FROM TETRAMETHYLTIN IN ALOW-PRESSURE GLOW-DISCHARGE DIODE REACTOR

Semiconducting thin films were obtained from a mixture of Ar + TMT (te tramethyltin) + O2 in an r.f. glow discharge diode reactor at low pres sure (10-100 Pa). Different substrates were used: glass, quartz, polym er (PP, PE) silicon and SiO2. Emission spectroscopy was employed to es timate the energetic character of the discharge and to characterize th e excited species in the plasma phase. Different surface diagnostic te chniques (profilometry, X-ray photoelectron spectroscopy (XPS), Fourie r transform IR (FTIR), scanning electron microscopy (SEM), four-point probe measurements, optical transmission) reveal the formation of carb on-free non-stoichiometric tin oxide films with perfectly controlled c onductivities varying from 10(-4) up to 10(2) S cm-1. The films examin ed by interface capacity measurements were n type semiconductors with a carrier concentration ranging between 10(15) and 10(17) cm-3 and a b and gap measured by optical transmission varying between 3.5 and 4 eV. The conductivity of the films can be improved by either annealing in nitrogen gas or hydrogen plasma post-treatment, as a result of changes in the chemical and physical structure of the films. Finally a mechan ism for the decomposition of TMT is proposed.