Origin of stress in radio frequency magnetron sputtered zinc oxide thin films

Abstract

Highly c-axis oriented ZnO thin films have been deposited on silicon substrates by planar rf magnetron sputtering under varying pressure (10-50 mTorr) and oxygen percentage (50-100%) in the reactive gas (Ar þ O 2) mixture. The as-grown films were found to be stressed over a wide range from À1 Â 10 11 to À2 Â 10 8 dyne/cm 2 that in turn depends strongly on the processing conditions, and the film becomes stress free at a unique combination of sputtering pressure and reactive gas composition. Raman spectroscopy and photoluminescence (PL) analyses identified the origin of stress as lattice distortion due to defects introduced in the ZnO thin film. FTIR study reveals that Zn-O bond becomes stronger with the increase in oxygen fraction in the reactive gas mixture. The lattice distortion or stress depends on the type of defects introduced during deposition. PL spectra show the formation of a shoulder in band emission with an increase in the processing pressure and are related to the presence of stress. The ratio of band emission to defect emission decreases with the increase in oxygen percentage from 50 to 100%. The studies show a correlation of stress with the structural, vibrational, and photoluminescence properties of the ZnO thin film. The systematic study of the stress will help in the fabrication of efficient devices based on ZnO film. V

High-Quality, Ultraconformal Aluminum-Doped Zinc Oxide Nanoplasmonic and Hyperbolic Metamaterials

“…Information about the defect concentration of ZnO‐based materials can be inferred by examining the visible portion of the PL emission spectrum. The most commonly referred defects in ZnO are oxygen vacancies (V o ), zinc interstitials (Zn i ), oxygen interstitials (O i ), oxygen antisites (O Zn ), and zinc vacancies (V Zn ) . V o and Zn i are known to be electron donating whereas O i , V Zn , and O Zn are found to be electron accepting.…”

Origin and role of elasticity in the enhanced DMMP detection by ZnO/SAW sensor

“…While at high pressure (≥30 mT), the energy of the ionic species on substrate surface is small due to extensive collision in the plasma. Hence possibility of atoms to be absent from the lattice point increases since mobility of the ad-atoms is less on the substrate surface and they do not have sufficient energy to be in the equilibrium position [21]. The crystallite size of ZnO thin films increases from 9 to 17 nm with increase in sputtering pressure from 10 to 20 mT and then decreases to 13 nm with further increase in sputtering pressure to 40 mT (Table 2).…”

Tunable synthesis and multifunctionalities of Fe3O4–ZnO hybrid core-shell nanocrystals

“…In Fig. 9b, the strong absorption at $443.5 cm À1 as indicated by the solid triangle evidently manifests the vibration of the Zn-O bonding [10,11,[52][53][54]. Other two characteristic peaks near to each other at $586.2 cm À1 and $617.1 cm À1 , as labeled by the filled circle, are attributed to the vibrations of the Fe-O bonding [55][56][57].…”