Field-Emission Characteristics of Al-Doped ZnO Nanostructures Hydrothermally Synthesized at Low Temperature

Abstract

The aluminum-doped ZnO (AZO) nanostructures with different Al concentrations were synthesized on AZO/glass substrate via a simple hydrothermal growth method at a temperature as low as 85 degrees C. The morphologies, crystallinity, optical emission properties, and chemical bonding states of AZO nanostructures show evident dependence on the aluminum dosage. The morphologies of AZO nanostructures were changed from vertically aligned nanowires (NWs), and NWs coexisted with nanosheets (NSs), to complete NSs in respect of the Al-dosages of 0-3 at.%, 5 at.%, and 7 at.%, correspondingly. The undoped ZnO and lightly Al-doped AZO (< or = 3 at.%) NWs are single-crystalline wurtzite structure. In contrast, heavily Al-doped AZO sample is polycrystalline. The AZO nanostructure with 3 at.% Al-dosages reveals the optimal crystallinity and less structural defects, reflecting the longest carrier lifetime and highest conductivity. Consequently, the field-emission characteristics of such an AZO emitter can exhibit the higher current density, larger field-enhancement factor (beta) of 3131, lower turn-on field of 2.17 V/microm, and lower threshold field of 3.43 V/microm.

pH‐Sensing Characteristics of Hydrothermal Al‐Doped ZnO Nanostructures

“…In the previous investigations [23,24], the AZO nanostructures with various Al dosages were synthesized successfully on AZO/glass substrate by hydrothermal growth method at 85 ∘ C. The morphologies, crystallinity, optical emission properties, bonding states, and chemical compositions of AZO nanostructures show evident dependence on the Al dosage [24]. While the Al dosage was equal or less than 3 at.%, only NWs are observed.…”

“…7 at.%) NSs reveal the polycrystalline ZnO wurtzite crystals. The optical emission properties of undoped ZnO and AZO nanostructures examined by photoluminescence (PL) spectra can be linked to the structural defects [24]. Less structural defects existed in the AZO NWs with appropriate Al dosage (i.e., 3 at.%).…”

“…Furthermore, Al atoms may also have more opportunities to occupy the sites of oxygen vacancies in the AZO NWs, associated with the decreased concentration of oxygen vacancies [19]. The experimental compositions of Al in the AZO nanostructures were analyzed as 0 at.%, 0.31 at.%, 0.81 at.%, 1.98 at.%, 3.35 at.%, and 6.27 at.% by X-ray photoelectron spectroscopy (XPS, Physical Electronics PHI-1600) [23,24], according to the controlled Al dosages of 0 at.%, 1 at.%, 2 at.%, 3 at.%, 5 at.%, and 7 at.% in the precursor solutions.…”

Uniform ZnO nanowire arrays: Hydrothermal synthesis, formation mechanism and field emission performance

“…Compared with these methods, hydrothermal process, with the advantages of mild reaction conditions, environment-friendly, and easy to control, is a potential and effective way to synthesize ZnO nanowires. Currently, 1D ZnO nanostructures (undoped and doped) such as nanoneedles [18], nanorods [19], nanobelts [20], nanowires [21,22,23] have been successfully synthesized by hydrothermal method. However, to the best of our knowledge, the low temperature hydrothermal synthesis of ZnO and AleZnO nanowire arrays and related field emission performances has been less reported.…”

Unique visible-light-assisted field emission of tetrapod-shaped ZnO/reduced graphene-oxide core/coating nanocomposites

“…Control of the surface’s geometrical morphology by sharpening the nanotapers or by using coatings with sharp-tipped nanoneedles and with amorphous C, CN x , and NiO films have been investigated in order to improve the field-emission current density891011. The doping of ZnO with group III (Al, In, and Ga) or group IV (Sn and Pb) elements also offer an effective approach to improving the conductivity of ZnO and their field-emission characteristics1213. Especially, photo-assisted field-emission techniques have attracted a great deal of attention because a high emission current density can be achieved by using such techniques1415.…”