Structural, electrical and optical properties of yttrium-doped ZnO thin films prepared by sol–gel method

Abstract

Yttrium-doped ZnO thin films were deposited on silica glass substrates by the sol–gel method. The structural, electrical and optical properties of yttrium-doped ZnO thin films were investigated systematically and in detail. All the thin films have a preferred (0 0 2) orientation. When compared with the electrical resistivity values of films without annealing treatment, the values of films annealed in the reducing atmosphere were decreased by about three orders of magnitude. The lowest electrical resistivity value was 6.75 × 10−3 Ω cm, which was obtained in the 0.5 at% yttrium-doped ZnO thin film annealed in nitrogen with 5% hydrogen at 500 °C. In room-temperature photoluminescence (PL) spectra, two PL emission peaks are found in the pure ZnO thin film; one is the near-band-edge (NBE) emission at 3.22 eV and the other is a green emission at about 2.38 eV. Nevertheless, the green emission is not found in the PL of the yttrium-doped ZnO thin films. The low-temperature PL spectrum of the undoped ZnO thin film at 83 K is split into well-resolved free and bound excition emission peaks in the ultraviolet region, but the NBE emission of the 5 at% yttrium-doped ZnO thin film at 83 K has only one broad emission peak.

An enhanced gas ionization sensor from Y-doped vertically aligned conductive ZnO nanorods

“…Naturally, both substitutional and interstitial Y dopants were present in the one-pot hydrothermal synthesized ZnO NRs. However, it is the substitutional Y 3+ ions responsible for the expansion of the crystal lattice constant due to the larger ionic radius of Y 3+ (0.92 Å) with respect to Zn 2+ (0.74 Å) [43], an observation consistent with the literature [40,44]. Additional evidence for the substitutional Y 3+ responsible for the expansion of the ZnO lattice constant was demonstrated from the gradual shifting of electron binding energy of Zn 2+ and O 2-as a function of Y doping concentrations [45].…”

“…Previous dip coating experiments showed similar effects using YCl 3 [40], hence negatively charged Y 3+ complexes are likely responsible for the shape of the YZO NRs by bonding to the positively charged ZnO (100) plane [41]. Similar behavior has been reported for other X 3+ ions, including Al 3+ , Ga 3+ and In 3+ [41].…”

“…The interstitial Y atoms will segregate at the crystal domain boundaries, reduce the crystal domain size and increase the structural disorder, which was confirmed by the XRD measurement. More importantly, the interstitial Y atoms are electrically inactive or even act as 'electron traps', which effectively passivate existing donors [40]. Thus the resistivity will increase with Y dopant concentration above a certain threshold (0.10 at%), accompanied by the reduction of crystal domain size.…”

Effects of the Cu Ion on the Structural and Optical Properties of Yttrium Doped ZnO by Solution Combustion

“…5 also it is observed that the UV-NBE emission of the samples is diminished by increasing Cu 2+ ion concentration, indicating that the optical-gap of ZnO semiconductor can be tailored by means of Cu 2+ doping. This last result can be technologically applied in UV radiation sensors fabrication [26].…”

Nb-doped ZnO transparent conducting films fabricated by pulsed laser deposition

“…As an intrinsic n-type semiconductor having a hexagonal wurtzite structure with a wide direct band gap of 3.37 eV at room temperature (RT) [12], ZnO could realize a lower resistivity via impurity-doping, such as Group IIIA (e.g., B, Al, Ga and In) [2][3][4]13,14], IVA (e.g., Si, Ge and Sn) [15], IIIB (e.g., Sc and Y) [16,17], and IVB (e.g., Ti and Zr) [18,19] elements. Impurity-doped ZnO thin films have been prepared by various techniques, such as molecular beam epitaxy (MBE) [13], metalorganic chemical vapor deposition (MOCVD) [7], pulsed laser deposition (PLD) [20,21], magnetron sputtering [14,16,18], thermal evaporation [22], spray pyrolysis [23] and sol-gel processing [17]. Among the fabrication techniques, pulsed laser deposition provides several advantages for growing high-performance TCO films [20,21].…”