7 NWs on the Si(110)
surface. Methods The experiments were performed in an ultra-high vacuum molecular beam epitaxy-STM system (Multiprobe XP, Omicron, Taunusstein, Germany) with a base pressure of less than 5.0 × 10−11 mbar. Substrates ABT 737 used for the deposition were cut from a phosphorus-doped, n-type Si(110) wafer with resistivity of approximately 0.01 Ω cm and have a size of 12 × 2.5 × 0.3 mm3. Atomically clean Si(110)-16 × 2 surfaces were prepared by degassing the substrates at about 600°C for 12 h, followed by flashing to 1,200°C and annealing at 600°C for 10 min. Mn was deposited on the Si(110)-16 × 2 surfaces by heating Mn lumps (purity 99.999%) in a Mo crucible with electron bombardment. The Mn flux was monitored by an internal ion collector mounted near the evaporation source. The deposition rate was controlled from approximately 0.01 to 0.5 ML/min (1 ML = 1 metal atom per 1 × 1 surface mesh = 4.78 × 1014 Mn atoms/cm2) [3]. During selleck inhibitor deposition, the substrates were heated by radiation from a tungsten filament located at the back of the sample holder. The temperature was set from 450°C to 600°C and measured using a thermocouple. An electrochemically etched tungsten tip was used for scanning. All STM images were recorded
at room temperature (RT) with a bias voltage of 2 to 3 V and a tunneling current of 0.1 to 0.2 nA. A backscattered electron Arachidonate 15-lipoxygenase scanning electron microscope (BE-SEM)
(Nova NanoSEM 230, FEI, Hillsboro, OR, USA) was used to ex situ observe the elemental distribution of the samples on a large scale. Results and discussion Effects of growth parameters on the formation of NWs Figure 1a shows STM images of the atomically clean Si(110) surface obtained by the well-established degassing, flashing, and annealing procedures. The high-resolution image (inset) clearly shows that the surface consists of equally spaced and alternately bright and dark buy PF-6463922 zigzag chains parallel to the direction, which is the typical characteristic reported for the Si(110)-16 × 2 reconstructed surface [25]. The bright and dark zigzag chains correspond to the upper and lower atomic layers of the Si(110) plane, respectively. The step height between the layers is 1.92 Å. A 16 × 2 unit cell is outlined by a rectangle in the inset. Figure 1 STM images of the Si(110) surface and the manganese silicide NWs grown on it. (a) STM images (500 × 500 nm2) of a clean Si(110) surface. The inset is a high-resolution STM image (30 × 30 nm2) showing the 16 × 2 reconstruction of the surface. A 16 × 2 unit cell is outlined by a rectangle. (b) STM image (1,600 × 1,600 nm2) of manganese silicide NWs and islands grown by depositing 1 ML Mn on the Si(110) surface at 585°C. During deposition, the deposition rate was kept at approximately 0.02 ML/min.