Size-controlled growth of ZnO nanowires by catalyst-free high-pressure pulsed laser deposition and their optical properties

Abstract

Single crystalline ZnO nanowires were fabricated on Si (100) substrates by catalystfree high-pressure pulsed laser deposition. It is found that the nanowires start to form when the substrate temperature and growth pressure exceed the critical values of 700 o C and 700 Pa, and their size strongly depends on these growth conditions. That is, the aspect ratio of the nanowires decreases with increasing temperature or decreasing pressure. Such a size dependence on growth conditions was discussed in terms of surface migration and scattering of ablated atoms. Room-temperature photoluminescence spectrum of ZnO nanowires shows a dominant near-band-edge emission peak at 3.28 eV and a visible emission band centered at 2.39 eV. Temperature-dependent photoluminescence studies reveal that the former consists of the acceptor-bound exciton and free exciton emissions; while the latter varies in intensity with the aspect ratio of the nanowires and is attributed to the surface-mediated deep level emission.

Effect of SiO2 Spacer-Layer Thickness on Localized Surface Plasmon-Enhanced ZnO Nanorod Array LEDs

“…In Figure 2(a), one can see that all spectra consist of a near-band-edge (NBE) emission peak at 380 nm and a relatively weak and broad deeplevel (DL) emission band centered at 560 nm. 30 Herein, the DL emission band is very likely induced by the surface defects of synthesized ZnO nanorods (e.g., oxygen vacancies) due to the relatively large aspect ratio of the nanorods. 14,25 The ZnO UV PL is enhanced even though the Ag NPs are directly coated onto the bare ZnO NRA.…”

Toward the Growth of Self-Catalyzed ZnO Nanowires Perpendicular to the Surface of Silicon and Glass Substrates, by Pulsed Laser Deposition

“…Many PLD process parameters affect the growth of the ZnO NWs, such as substrate temperature, gas pressure, and the substrate–target distance. The deposition temperature has a critical effect on surface diffusion [ 26 , 51 , 60 , 61 , 62 ]. If it is too low <200 °C, the deposited ZnO will not have enough mobility to reach nucleation sites, and would rather increase the roughness of the surface [ 63 ].…”

“…It is also used to produce various nanostructures like nanorods [ 38 , 39 , 40 , 41 , 42 ], nanoparticles [ 41 , 43 , 44 , 45 ], and nanowalls [ 46 ]. A survey [ 26 , 47 , 48 , 49 , 50 , 51 , 52 , 53 , 54 , 55 , 56 , 57 ] of the synthesis parameters of ZnO NWs by PLD is presented in Table 1 presenting the growth parameters such as the type of seed layer, temperature, pressure, and distance between substrate and target. It is noticed that growth temperature varies between 500 and 900 °C, pressure > 1 Torr, and relatively short target–substrate distance <3 cm.…”

Probing the highly efficient room temperature ammonia gas sensing properties of a luminescent ZnO nanowire array prepared via an AAO-assisted template route

“…In general, most of the reported ZnO nanostructures with different diameters and lengths are synthesized by various methods like solid-liquidvapor processes, metal-organic chemical vapor deposition, pulsed laser deposition, wet chemical methods and templateassisted methods. [18][19][20][21][22] Recently, the AAO-template route has been the most impressive way because of its low growth temperature and good potential for large scale synthesis of ordered nanostructures. [23][24][25][26][27][28] The photoluminescent properties of ZnO have received much attention because of the ability to tune the optical properties of ZnO by tailoring its band gap (direct band gap of 3.37 eV) with higher exciton binding energy (60 meV) as compared to other semiconductor materials such as ZnSe (22 meV), ZnS (40 meV) and GaN (25 meV) which make it suitable for short-wavelength optoelectronic devices and gas sensor applications.…”