STM investigation of cobalt silicide nanostructures’ growth on Si(111)-(√19 × √19) substrate

Abstract

Continuing miniaturization of electronic devices necessarily requires assembly of several different objects or devices in a small space. Therefore, besides thin films growth, the possibility of fabricating wires and dots [1, 2] at the nanometre scale composed of metal silicides is of the top interest. This report is about the STM/STS investigation of cobalt silicides’ nanostructures created on Si(111)-(√19 × √19) substrates via Co evaporation and post deposition annealing. This (√19 × √19) reconstruction was induced by Ni doping. Less than 1ML of Co on surface was obtained. Surface reconstruction induced growth of agglomerates of clusters rather than an uniform layer. The post deposition annealing of a crystal sample (up to 670 K, 770 K, 870 K, 970 K, 1070 K and 1170 K) led to creation of silicides’ nanostructures. Measurements showed that coalescence of Co nanoislands begun around 970 K. Annealing above 1070 K led to alloying of a Co, Ni and Si. As a consequence the Si(111)-(7×7) reconstruction occurred at the cost of Si(111)-(√19 × √19).

Investigation of semiconductor properties of Co/Si(111)-7 × 7 by AFM/KPFS

“…It is induced by the generation of holes at an inversion state when the positive sample bias is sufficiently larger. The band gap of Co-RC reconstruction (see figure 4(d)) is approximately 1.5 V by the ∆f -bias response in our KPFS measurement, which is consistent with the STS result [52]. To summarize the above results, the semiconductor property of Co-RC reconstructions was identified by KPFS.…”

“…Thus, a larger depletion layer width is induced by 1 ML Co cluster on Si(111). This result is in good agreement with the band gap of Co-RC and Si(111)-√7×√7-Co surface [51,52]. Namely, the band gap is larger when the Co doping density is higher.…”

“…In our previous work, we have found interstitial Co atom adsorption and individual ring-like clusters (RCs) on a Si(111)-7 × 7 surface at a low Co coverage [46]. Moreover, many types of Co-induced reconstruction are observed in the case of high Co coverage and high-temperature annealing [47][48][49][50][51][52]. For example, several Co-induced reconstructions coexist on a Si(111) substrate [40,53].…”

“…For example, several Co-induced reconstructions coexist on a Si(111) substrate [40,53]. Most of the previous studies focused on the atomic structures and electrostatic properties of Co clusters and reconstructions [47][48][49][50][51][52][53][54], the semiconductor properties of Co-RC and Si(111)-√7 × √7-Co R 29.1 • reconstruction were identified by the large bad gap in STS experiments [51,52]. Moreover, the 2D CoSi 2 island reveals the metal properties due to shifts in the energy levels [10], a similar behavior was shown on 2D TMDCs, such as cobalt disulphide (CoS 2 ) [55].…”

Shape-Controlled Fabrication of Micro/Nanoscale Triangle, Square, Wire-like, and Hexagon Pits on Silicon Substrates Induced by Anisotropic Diffusion and Silicide Sublimation

“…investigated the thermal stability of CoSi 2 and measured the relevant resistance . However, so far there have been few studies focusing on the nanoscale Si−Co interaction. ,− Recently, Chen et al . investigated the growth kinetics of nanoscale Co silicide via point-contact reactions between Co nanodots and Si nanowires.…”