Low temperature selective growth of GaN single crystals on pre-patterned Si substrates

Abstract

We report on a hybrid method for fabrication of arrays of GaN nanocrystals by low-temperature UHV selective growth on pre-patterned silicon substrates covered by native oxide. Patterning of the substrates was performed by using a gallium focused ion beam (FIB). To get GaN nanocrystals at specific positions, Ga droplets were created at FIB patterned sites by evaporation of Ga atoms at 280°C substrate temperature first, and then modified by their post-nitridation using an ultra-low energy (50 eV) nitrogen ion-beam at a sample temperature of 200°C. To get larger arrays of GaN nanocrystals (≈150 nm and 200 nm in diameter), such a sequential process was repeated in several cycles at slightly modified operation conditions. The quality of the nanocrystals was checked by measurement of their photoluminescence properties which proved the occurrence of the peak of a band edge emission at around 367 nm (3.38 eV).

Low temperature 2D GaN growth on Si(111) 7 × 7 assisted by hyperthermal nitrogen ions

“…Secondly, subsequent nitridation leads to a transformation of Ga droplets into GaN nanocrystals. This process is described in detail in [20] and also in our paper [21]. The size and density of Ga droplets on the Si(111) 7×7 surface can be controlled both by the surface temperature and deposition time [22].…”

“…The fitting parameters of the Ga 2p 3/2 peak were reported in ref. 21 . The inserted AFM image of a Ga droplet clearly shows that this droplet is not fully transformed into 2D GaN.…”

“…20 and also in our paper. 21 The size and density of Ga droplets on the Si(111) 7 Â 7 surface can be controlled both by the surface temperature and deposition time. 22 Ga deposition on Si(111) 7 Â 7 was carried out for 50 min (resulting in a coverage of 5 ML) at 330 C. The density of gallium droplets spread over the Si(111) 7 Â 7 surface was approximately 3 Â 10 8 droplets per cm 2 .…”

Chiral Nanoparticle Chains on Inorganic Nanotube Templates

“…Figure 3c,d shows WS 2 nanotubes decorated with gallium and germanium nanoparticles, which were deposited by evaporation of the respective elemental materials under high-vacuum conditions onto nanotubes dispersed over a solid substrate (silicon). Note that gallium could be subsequently oxidized to form gallium oxide, nitrided to form gallium nitride, 58 or exposed to group V atomic flux to form III−V semiconductor (see Figure S9e, showing XPS analysis of WS 2 nanotubes decorated by GaAs nanoparticles), thus widening the portfolio of available nanoparticles. There are no limitations other than the deposition temperature that would prevent other techniques like atomic layer deposition 59 or chemical vapor deposition 60 from being used for creation of chiral nanoparticle assemblies utilizing these inorganic templates.…”