engleski

Investigation of residual chlorine in TiO2 fi lms grown by atomic layer deposition

Among metal-oxide semiconductors, titanium dioxide (TiO2) is one of the most promising materials for many applications, ranging from microelectronics to photo catalysis or medical device materials. In recent years, Atomic Layer Deposition (ALD) technique has been extensively used for the growth of thin TiO2 fi lms. The main advantages of ALD are excellent thickness control and the high conformity of the obtained fi lms. In comparison with the conventional thermal ALD, plasma-enhanced ALD (PEALD) enables the higher growth rate at reduced substrate temperatures, which is especially important for the growth of thin fi lms on temperature sensitive materials. In the case when titanium tetrachloride (TiCl4) is used as the ALD precursor for the synthesis of thin TiO2 fi lms, some chlorine impurities remain present in the resulting inorganic material. The assessment of Cl impurities is particularly important for the photocatalytical applications where the incorporated chlorine lowers the energy gap of TiO2, thus enabling its absorption to higher wavelength, or aff ecting performances of the TiO2-based catalytic systems including fuel cells, alkane dehydrogenation and water splitting systems and lithium−O2 batteries. In the present work we present a comprehensive study of residual chlorine impurities within the TiO2 fi lms grown on silicon substrates using ALD and PEALD techniques at a wide temperature range. By using plasma, it was possible to signifi cantly lower the deposition temperatures and achieve better quality of fi lms with lower amount of impurities. We have employed Secondary Ion Mass Spectrometry for the in-depth elemental analysis and the determination of the thickness of TiO2 layers, while chemical bonding of Cl was determined from X-ray Photoemission Spectroscopy measurements. In addition, the surface topography, conformity, composition and fi lm thickness was studied with Scanning Electron Microscopy.

Titanium dioxide ; Atomic layer deposition ; Residual chlorine ; Thin films ; Crystallization

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