Methods The samples discussed here are fabricated using solid-source molecular beam epitaxy on (001) GaAs substrates with a valved cracker cell for As4 supply. The Ga flux is adjusted for a GaAs growth rate of 0.8 monolayers (ML)/s.

The As flux during GaAs buffer layer growth corresponds to a flux gauge reading of 1 ×10−5 Torr. During droplet etching, the As flux is minimized to less than 1 ×10−7 Torr by closing the As valve, the As cell shutter GW3965 nmr and in addition the main shutter in front of the sample during annealing. After growth of a 100-nm-thick GaAs buffer layer at a temperature T = 600℃ to smooth the surface, the As shutter and valve are closed and the temperature is increased to the annealing temperature of 630℃ to 670℃. Ga is the deposited for 2.5 s corresponding to a droplet material coverage θ= 2.0 ML. After deposition of the droplet material, the initial droplets are transformed into nanoholes during post-growth annealing for a time t a. After annealing, the samples are quenched by switching off the substrate heater. Figure 1a shows a sketch of the whole process including the shape modification of the droplet etched nanoholes during long-time annealing,

and Figure 1b,c displays typical atomic force microscopy (AFM) images visualizing the different stages. Results and discussions The purpose of this study is to examine droplet N-acetylglucosamine-1-phosphate transferase etching processes at high temperature. Previously, the generation of nanoholes by LDE with Ga droplets has been demonstrated in the temperature regime between 570℃ and Gamma-secretase inhibitor 620℃

[13]. Figure 2a,b establishes that droplet etching with Ga on GaAs is histone deacetylase activity possible also above the congruent evaporation temperature of 625℃ [21, 22]. The holes have an average depth of 68 nm at T = 650℃ (Figure 2c) which is more than four times deeper compared with previous Ga-LDE results [13]. A summary of the temperature-dependent structural characteristics of the nanoholes is plotted in Figure 2d. The hole density N decreases with T in accordance with previous results on Ga- [13] or Al-LDE [23]. A particularly interesting observation is that the holes have very low densities (≃106 cm −2). This demonstrates that high T droplet etching can be used to generate low-density nanohole templates for the subsequent creation of well-separated nano-objects following deposition. The hole diameter increases with T, which is related to the increasing volume of the initial droplets V≃θ/N at conditions with reduced density N. Also, the hole depth increases with T. This temperature-dependent trend of hole depth is in agreement with previous experimental results [13, 23] and has been modelled by a simple scaling law with a temperature-dependent etching rate [23].