UV Absorptance of Titanium Dioxide Thin Films by Plasma Enhanced Deposition from Mixtures of Oxygen and Titanium-Tetrakis-Isopropoxide

Abstract

A low pressure radio frequency discharge was used to deposit films by mixtures of oxygen and titanium (IV) isopropoxide (TTIP) at powers of 200 W on films of polyethylene-terephthalat and samples of quartz glass. In the non-thermal plasma, films of rather pure TiO 2 could be deposited as revealed by X-ray photo-electron spectroscopy. Besides the film growth rate and the chemical composition, the spectral behaviour of the spectral transmittance of visually transparent films was determined in the range from 200 to 500 nm. Furthermore, the absorptance of films has been derived at characteristic spectral positions of the transmission spectra of the films. Accordingly, cut-off wavelength was found to increase with deposition time from 5 to 10 min as well as with the concentration of TTIP in a range below 1.7%. At 310 nm, the spectral absorption coefficient (extinction coefficient × concentration) was 12 µm −1 . While keeping other parameters constant, this coefficient decreased by 4 µm −1 due to an increase of the concentration of TTIP from 1.7% to 8%. Simultaneously, the surface roughness increased as revealed by profilometry. Thus, since the chemical structure of films was found to change only marginally, a decrease of the film density is likely to cause the observed dependence of the absorption coefficient with increasing precursor concentration.

Low temperature temporal and spatial atomic layer deposition of TiO2 films

“…52,53 Since there is no Ti-C bond in the TTIP precursor, the formation of a Ti-C bond can be due to the reducing effect of the sputtering prior to the XPS measurement. The same effect was observed by Sonnenfeld et al 54 Lack of Ti-C bonds in the same samples before sputtering also supports the idea of the reducing effect during sputtering. The C1s peak of the films deposited by plasma shows a peak at binding energy of 288.8 eV in addition to the peak at 284.7 eV [ Fig.…”

Enhancement of metal oxide deposition rate and quality using pulsed plasma-enhanced chemical vapor deposition at low frequency

“…However, the precursor that requires activation is O 2 , as its 5 eV bond strength renders it inert to many organometallics. 15,16,18 The results presented here suggest that plasma activation of the metal precursor may be detrimental to both deposition rate and film quality. In Fig.…”

“…[15][16][17] The former condition reflects the inert nature of O 2 with many metal precursors at the low temperature and pressure that characterize PECVD systems. 15,16,18 The latter is achieved by operating at extreme levels of dilution so that the precursor is oxidized in the plasma before it can be transported to the substrate. In this article we demonstrate that pulsed operation is also beneficial for conditions that result in deposition during continuous wave ͑cw͒ operation.…”

Effect of wall conditions on the self-limiting deposition of metal oxides by pulsed plasma-enhanced chemical vapor deposition

“…Unlike water or ozone, molecular oxygen is unreactive with certain organometallic precursors, particularly at the low pressures and temperatures employed in PECVD. 5,6,19 While both ALD and pulsed PECVD provide self-limiting growth, the mechanisms involved are completely different. ALD relies on the use of kinetically limited half reactions.…”