Changing vacancy balance in ZnO by tuning synthesis between zinc/oxygen lean conditions

Abstract

The nature of intrinsic defects in ZnO films grown by metal organic vapor phase epitaxy was studied by positron annihilation and photoluminescence spectroscopy techniques. The supply of Zn and O during the film synthesis was varied by applying different growth temperatures (325–485 °C), affecting decomposition of the metal organic precursors. The microscopic identification of vacancy complexes was derived from a systematic variation in the defect balance in accordance with Zn/O supply trends.

Understanding phase separation in ZnCdO by a combination of structural and optical analysis

“…In its turn, the decomposition of precursors is governed by the substrate temperature. Thus, exploring the limits of Cd incorporation into w-ZnO, Zn-lean growth conditions 18 found in temperature-variation experiments were applied to maximize Cd content in w-ZnCdO. Further, flow-variation experiments were performed using this optimal Zn-lean condition.…”

“…19 Note that XRD features of zb-ZnO appears to be close to those of rs-CdO, with characteristic (002) and (111) peaks at 2θ = 39.50 • and 34.00 • , respectively. [15][16][17][18][19][20][21] PL properties of the samples were investigated at 10 K and 300 K employing a 325-nm-wavelength cw He-Cd laser with an output power of 10 mW as an excitation source. The emission was collected with a microscope and directed to an imaging spectrometer (HORIBA Jobin Yvon, iHR320) equipped with an electron multiplying charge-coupled device (EMCCD) camera (Andor DL-658M) and also to fiber-optic spectrometers (Ocean Optics, HR4000 and USB4000) with 0.2-and 2-nm spectral resolutions, respectively.…”

“…Indeed, Zn/O lean/rich conditions during MOVPE ZnO synthesis may be readily provided by changing the efficiency of DEZn and t-BuOH decomposition solely by tuning the growth temperature. 18 Literally, the pyrolysis of DEZn starts at ∼300 • C and completes at temperatures 385 • C. On the other hand, oxidizing capacity of t-BuOH lasts until ∼450 • C. Considering the arguments above, in the context of measurements illustrated in Figs. 1-4, it is likely we have used Zn lean conditions in the low-temperature recipes in our samples.…”

“…The increase in the growth temperature leads to an apparent retardation of Cd incorporation due to the lack of vacant sites, which are instead readily occupied by Zn. Note, however, that increasing of the temperature above 430 • C results in oxygen-lean conditions, 18 and the chemical electronegativity difference between Zn and Cd may limit the incorporation of Cd too. Also, at higher temperatures Cd may desorb from the surface as it is known to be a very volatile element.…”

Zn-vacancy related defects in ZnO grown by pulsed laser deposition

“…There have been relatively more PAS studies on the ZnO single crystals [20,22,[25][26][27][28][29] and several on ZnO nanostructures [15,30] to identify the V Zn -related defects and their thermal evolutions in these materials. Although device applications usually involve the use of ZnO materials in the form of thin films deposited on substrates, PAS studies on ZnO thin films are relatively few [31][32][33][34] and the understanding of V Zn -related in ZnO films is far from complete.…”