Chemical Passivation of Silicon Nanowires with C₁−C₆ Alkyl Chains through Covalent Si−C Bonds

Abstract

We report on the functionalization of Si NWs with C 1 -C 6 alkyl chains using a versatile two step chlorination/ alkylation process. We show that Si NWs terminated with C 1 -C 6 molecules, through Si-C bonds, connect alkyl molecules to 50-100% of the Si atop sites and provide surface stability that depends on the chain length and molecular coverage, according to the following order: COur results indicate that the oxidation resistance of (C 1 -C 2 )-Si NWs is significantly higher than equivalent 2D Si(100) surfaces, whereas (C 3 -C 6 )-Si NWs are comparable to 2D (C 3 -C 6 )-Si(100). These discrepancies can be explained as follows: the lower the molecular coverage, the higher the probability for interaction between oxidizing agents (O 2 or H 2 O) and molecule-free sites. Our results are of practical importance when reduced amounts of oxide are required, e.g., for radial epitaxy on NWs to realize vertical P-N junctions for solar cells or for radial Si/Ge superlattices for application in optoelectronics.

Covalent Attachment of Alkyl Functionality to 50 nm Silicon Nanowires through a Chlorination/Alkylation Process

“…The alkylation rate of the short alkyl chains (C 1 -C 6 ) 52 at alkylation processes <100 min was higher than those for long alkyl chains (C 8 -C 10 ). The times required to achieve 92 ( 3% of the saturation level of the various adsorption curves, Γ sat , together with the related C-Si/ Si2p ratios, are summarized in Table 1.…”

“…ref 57. XPS scans for Si NWs were employed and compared to that of 2D Si(100). 52 To determine the position/shift of the peaks, we have considered two main approaches: (I) the center-tocenter distances were fixed at 1.10 ( 0.10 eV between the C-Si and the C-C emissions and at 2.60 ( 0.10 eV between the C-O and the C-Si emissions; and (II) the center-to-center distance allowed flowing, while the full width at half-maximum (fwhm) was identical in Si NW and 2D Si(100) samples. XPS scans for Si NWs showed similar fwhm's for a Si-C bond compared to that of 2D Si(100).…”

“…In contrast, the C-O peaks can be attributed to adventitious carbonaceous materials that are physisorbed on top of the monolayer. 52,64,65 The emission at 285.20 ( 0.02 eV can be ascribed to adventitious C-C or C-H specimen that do not participate in the Si-C bond.…”

Silicon Nanowire Sensors Enable Diagnosis of Patients via Exhaled Breath

“…The high sensitivity, low-power consumption, fast-response times, and the compatibility with conventional silicon technology and readout circuitry, have the potential to get SiNW FETs to give us simple signal transductions of disease breathprints, as well as being amenable to miniaturization and scalability. [45][46][47][48][49][50] Results and Discussion…”

Fluorinated alkyne-derived monolayers on oxide-free silicon nanowires via one-step hydrosilylation

“…The center-to-center difference between the C-Si peak and the -CH 2 -CH 2 peak was 1.1 eV, as also observed in a previous study on Si NWs from Bashouti and co-workers. [46] Interestingly, we found that the center-to-center difference between the -CF 2 -CH 2 and -CH 2 -CH 2 peak was 1.3 eV, whereas for planar Si surfaces 0.9 eV was found. Also, the C-F peaks observed for Si NWs occur consistently at slightly higher values than observations for flat Si (111) surfaces.…”