Effect of Doping and Morphology on UV Emission in Low‐Dimensional ZnO:Na Structures

Abstract

Band-edge photoluminescence of zinc oxide materials reveals a phononassisted ultraviolet emission enhanced by Na doping. We report the synthesis of ZnO and Na-doped ZnO, the changes in structure and optical properties as a function of doping concentration and synthesis temperature. The obtained samples are nanoneedles, microparticles, and microwires. The structural effect of Na doping is studied by X-ray diffraction and Raman spectroscopy. Room temperature photoluminescence reveals a contribution of band bending at the surface of the nanostructures, decreasing with Na concentration. Franz-Keldysh effect predicts strong electric field localized in the depletion region and appears to be the cause of red-shift in UV band emission of nanoneedles in comparison to microwires. Our results indicate that Na doping introduces an acceptor level between 150 and 200 meV above the valence band.

Non-steady state transport of charge carriers. An approach based on invariant embedding method

“…We measured the conductivity for around 8:4 Â 10 4 s (%23:3 h), until it approximates the initial value of the excitation stage. 17,27 B. Model for the defect energy levels of the ZnO microwire…”

The s-d exchange model as the underlying mechanism of magnetoresistance in ZnO doped with alkali metals

“…Starting from ZnO powders doped with 5 at.% of Na or Li synthesized as described in [14], corresponding ceramic targets were fabricated. Then, high quality oxygen defi cient ZnO:Na and ZnO:Li thin films were grown on sap phire (0 0 0 1) substrates (dimensions: (5 × 5 × 0.5) mm 3 ) by pulsed laser deposition (PLD) at a temperature of 550 • C and an oxygen pressure between 0.05 and 0.5 mTorr using a Nd:YAG laser operated with a wavelength of 266 nm, a repetition rate of 10 Hz and an energy density of 2.1 J cm −2 [33].…”

“…Alternatively, it has been predicted that acceptor doping with nonmagnetic elements like Li or Na stabilizes the for mation of zinc vacancies V Zn [6,[12][13][14]. Moreover, recent works have proposed and also shown evidence of V Zn as local ized magnetic defects in ZnO [15,16].…”

“…Moreover, recent works have proposed and also shown evidence of V Zn as local ized magnetic defects in ZnO [15,16]. Doping of ZnO with Na or Li has been previously performed in a wide variety of micro and nanostructures in search of the development of optical and optoelectronic devices [6,[12][13][14][17][18][19][20][21][22]. It has been found that the optimal Li or Na doping that generates substitutional defects like Zn Li or Zn Na (which are the ones that stabilize the V Zn ) without producing a significant amount of interstitial ones (which are donors) is around 5 at.% [13,14].…”

“…Doping of ZnO with Na or Li has been previously performed in a wide variety of micro and nanostructures in search of the development of optical and optoelectronic devices [6,[12][13][14][17][18][19][20][21][22]. It has been found that the optimal Li or Na doping that generates substitutional defects like Zn Li or Zn Na (which are the ones that stabilize the V Zn ) without producing a significant amount of interstitial ones (which are donors) is around 5 at.% [13,14]. Above this concentration, interstitial doping starts to increase compensating the acceptor ones.…”