Investigations of gamma and X-ray radiation effects in
transparent and conductive oxides
G. Socol
1
, G. Dorcioman
1
, D. Craciun
1
, P. Garoi
1
, O. Fufa
1
, L. Truica
2
,
A. C. Galca
2
, H. Swart
4
, C. Martin
5
, V. Craciun
1,*
1
National Institute for Lasers, Plasma and Radiation Physics, Măgurele, Romania
2
National Institute for Materials Physics, Magurele, Romania
3
Horia Hulubei National Institute for Physics and Nuclear Engineering, Magurele, Romania
4
Free State University, Bloemfontein 9300, Republic of South Africa
5
Ramapo College, New Jersey, USA
Studies investigating the effects of radiation on the structure and properties of various
materials have been usually performed on single crystals or sintered pellets having large grain
sizes. Recently, more and more devices that are incorporating nanocrystalline or amorphous
transparent and conductive oxides (TCO) have been manufactured and tested. Investigations
of the effects of radiation on such nanostructured films have found interesting differences
such as better resistance to amorphization with respect to the results obtained for large
grains/polycrystalline films. The absence of a long distance order allows for short diffusion
distances of the irradiation created defects before encountering sites in the network that act as
sinks. Also, the bonding between metal and oxygen is ionic. Therefore, the optical and
electrical properties could be less affected by exposure to radiation. To investigate in detail
the gamma and X-ray radiation effects on TCO we used the Pulsed Laser Deposition (PLD)
technique, which is very suitable to grow nanocrystalline or amorphous thin films of almost
any materials starting from inexpensive targets. By changing the deposition parameters, films
possessing different chemical compositions and/or structures could be easily obtained. The
surface morphology of the deposited films is very smooth, allowing for the use of surface
sensitive characterization techniques such as X-ray reflectivity, X-ray diffuse scattering,
grazing incidence X-ray diffraction, X-ray photoelectron spectroscopy, or nanoindentation
that all possess depth resolutions of the order of few nm. The effect of gamma and X-ray
irradiation on the structure, desity, surface morphology, chemical composition, optical and
electrical properties of the typical TCO films, indium zinc oxide and indium gallium zinc
oxide with various In, Zn and Ga compositions were investigated and compared with those
obtained on polycrystalline films.
O 48
-114-
