Electrical and optical properties of W-doped ZnO films grownon (11\bar{2}0) sapphire substrates using pulsed laser deposition

Abstract

W x Zn 1¹x O films with various doping concentration were prepared using pulsed laser deposition (PLD) on the (11 20) face of sapphire. The c-axis-oriented W x Zn 1¹x O films were grown without in-plane rotation domains when the W content in the films was below 3.6 at.%. The films exhibit a high transmittance of approximately 80% in the visible-near infrared region regardless of the W content, and no shift of the absorption edge was observed. From the results of Hall measurements, it was revealed that the doping efficiency of W in the films was <0.15 electrons/W. The electron mobility of the W x Zn 1¹x O films was 1435 cm 2 V ¹1 s ¹1 , which is relatively low compared with that of the undoped ZnO film grown using PLD. The low doping efficiency and electron mobility are considered to be attributed to the formation of defects resulting from the W-doping.

n-Type conducting P doped ZnO thin films via chemical vapor deposition

“…The decrease in carrier concentration is attributed to self-compensating mechanisms, such as O interstitials or Zn vacancies that increase with increasing P levels in ZnO, and/or the formation of electrically inactive secondary phases such as Zn 3 P 2 or P 2 O 5 that were undetected by XRD and XPS. [45][46][47] The reduction in carrier mobility with increasing levels of P is due to increased ionized impurity scattering and increased secondary electrically inactive phase formation. There are numerous examples of the AACVD growth of cation doped ZnO using [Zn(OAc) 2 $2H 2 O] for TCO applications in the literature ( Table 2).…”

Face-selective tungstate ions drive zinc oxide nanowire growth direction and dopant incorporation

“…Tungsten is an appropriate dopant species for ZnO in terms of the ionic radius (Zn 2+ 60 pm, W 6+ 42 pm) and the coordination number (Zn 2+ (IV) and W 6+ (IV)). In fact, the improvement of molecular sensing property of ZnO thin film was previously demonstrated by W doping 40,41 . The nanowire growth was conducted by a seed-assisted hydrothermal approach in aqueous solution containing Zn(NO 3 ) 2 (Zn precursor), hexamethylenetetramine (HMTA), polyethyleneimine (PEI), and Na 2 WO 4 (W precursor).…”

Understanding W Doping in Wurtzite ZnO

“…These results clearly reveals that high W contents are achievable, a key matter when aiming at tuning the properties of ZnO which is also consistent with the experimental finding that doping with W achieved contents up to 15 at. % . Nevertheless, it is also important to realize that the behavior of the three different doping situations changes below 12.5 at.…”

“…Aside from considering V Zn and V O , the most likely defects in O- and Zn-rich conditions, respectively, according to previous LDA calculations, we consider here interstitial W (W i ) and W substituting lattice Zn (W Zn ) and O atoms (W O ). Notice that previous works contemplated interstitial oxygen (O i ) as a possible counter charge mechanism to W Zn , although it was found that V Zn is energetically more favorable than O i , and, therefore, O i has not been further considered. Further, note that even though the formation energetics is treated at the PBE level, former studies comparing V O formation in O-poor environments at different concentrations revealed mean unsigned variations of 0.29 eV when carrying out PBE or employing the PBE0 hybrid functional .…”

“…The appearance of V Zn would counteract the four extra electrons when having W Zn , and the concomitant contraction expected from the smaller ionic radius of the formally W 6+ cation would be counteracted by a lattice expansion due to the presence of V Zn . This charge compensation mechanism seems to be a current paradigm, which also serves to explain the reduced charge carrier efficiency W-doped ZnO, quantified to be below 0.15 e per W atom …”