Photoluminescence Study of the Influence of Additive Ammonium Hydroxide in Hydrothermally Grown ZnO Nanowires

Abstract

We report the influence of ammonium hydroxide (NH4OH), as growth additive, on zinc oxide nanomaterial through the optical response obtained by photoluminescence (PL). A low-temperature hydrothermal process is employed for the growth of ZnO nanowires (NWs) on seedless Au surface. A more than two order of magnitude change in ZnO NW density is demonstrated via careful addition of NH4OH in the growth solution. Further, we show by systematic experimental study and PL characterization data that the addition of NH4OH can degrade the optical response of ZnO NWs produced. The increase of growth solution basicity with the addition of NH4OH may slowly degrade the optical response of NWs by slowly etching its surfaces, increasing the point defects in ZnO NWs. The present study demonstrates the importance of growth nutrients to obtain quality controlled density tunable ZnO NWs on seedless conducting substrates.Electronic supplementary materialThe online version of this article (10.1186/s11671-018-2665-4) contains supplementary material, which is available to authorized users.

Evidence of Piezoelectric Potential and Screening Effect in Single Highly Doped ZnO:Ga and ZnO:Al Nanowires by Advanced Scanning Probe Microscopy

“…The prevalence of the surface effects is dependent upon the radius of ZnO nanowires and is strongly improved for typical values below 20 nm as reported by theoretical simulations in the case of the CBD method . In the present case, it should be noted that the growth of Al- and Ga-doped ZnO nanowires was achieved at a high pH value, where attractive electrostatic forces favor the incorporation of Al and Ga dopants. , It is well-known that the growth of ZnO nanowires at a high pH value is responsible for a strong increase in their surface roughness on the m -plane sidewalls and in the related density of defects. ,,− This has been explained by the strongly anisotropic growth rate favoring the fast elongation of ZnO nanowires as well as by erosion phenomena caused by HO – ions on their surface. In that sense, the surface trap density in ZnO nanowires grown at a high pH value is expected to be much larger than the typical value of 1–4 10 13 cm –2 obtained in the case of ZnO nanowires grown at a much lower pH value .…”

“…20,21 It is well-known that the growth of ZnO nanowires at a high pH value is responsible for a strong increase in their surface roughness on the m-plane sidewalls and in the related density of defects. 20,21,[61][62][63] This has been explained by the strongly anisotropic growth rate favoring the fast elongation of ZnO nanowires as well as by erosion phenomena caused by HOions on their surface.…”

Effect of the Precursor on the Synthesis of ZnO and Its Photocatalytic Activity

“…The morphology of the nano-ZnO differs significantly depending on the precursor used [36,37]. The addition of NH 4 OH during the synthesis process could affect the nucleation and growth of the ZnO, thereby influencing the crystal formation and morphological structure, which is associated with a supersaturation that affects the nuclei formation [38].…”

Modulating the growth of chemically deposited ZnO nanowires and the formation of nitrogen- and hydrogen-related defects using pH adjustment

“…ZnO NWs also possess the advantage to be grown by the low-temperature and low-cost solution route of chemical bath deposition (CBD), where their crystallization follows the thermally-activated dehydration of [Zn(H 2 O) 6 ] 2+ ions coming from the Zn(II) ions representing the limiting reactant at low pH, and where their growth is kinetically controlled by the thermally-activated decomposition of hexamethylenetetramine (HMTA) that slowly releases hydroxide ions in an aqueous solution. [6][7][8][9][10] Hence, the understanding of the different experimental parameters such as the chemical precursor concentration, 8,9,11,12 nature of the species present in the solution, 11,[13][14][15][16][17] pH of the solution, 11,18,19 temperature and growth time, 10,20 have shown to play a key role on the morphology, structural, chemical, optical, and electrical properties of ZnO NWs. Universally, the hydronium and hydroxide ions are referred to as the water ions,…”