Tailoring nanostructure of ZnO thin films by plasma assisted and Au-catalyst assisted MOCVD

The structural, morphological and optical properties of ZnO thin films grown by metal organic chemical vapor deposition (MOCVD) also plasma-assisted (PA-MOCVD) and Au-catalyst assisted (Au-MOCVD) are investigated. A new precursor Zn(TTA)2TMED (HTTA = 2-thenoyltrifluoroacetone, TMED = N,N,N′,N′-tetramethylethylendiamine) and O2 have been used to grow film on various substrates, including Si(1 0 0), α-Al2O3(0 0 0 1) and quartz. Spectroscopic ellipsometry is used for investigating the correlation between film nanostructure and optical properties (exciton of ZnO appears in dielectric function). It has been found that the O2 plasma assisted growth results in highly (0 0 0 1) oriented ZnO films on all investigated substrates, with better optical quality as indicated by a sharp and intense exciton in the dielectric function spectra. Conversely, highly textured and rough films are deposited by MOCVD and also using the Au-catalyst. In the latter case, coupling ZnO with Au nanoparticles used as catalyst results in an enhancement of the Au surface plasmon resonance peak at 2.2 eV.