Long-Term Stability and Electrical Performance of Organic Monolayers on Hydrogen-Terminated Silicon

Abstract

The long-term stability (gradual oxidation) of two structurally different organic monolayers, C6H5(CH2)3−Si (C3Ph−Si) and CH3(CH2)11−Si (C12−Si), covalently bonded to n-type silicon(111) was studied and correlated to the electrical performance of the thus formed mercury | monolayer | n-Si junctions. High-resolution XPS analysis of the O 1s region on freshly prepared samples identified physically adsorbed oxygen (Oad) and oxygen-containing species (SiO x ) bound to silicon at 532.2 and 533.5 eV, respectively. When left under ambient conditions, both bands increased in intensity as time progressed, while no change in the carbon content (C 1s peak) was observed. More importantly, upon aging, there was a noticeable increase in the electrical current flow of both <Hg|C12−Si> and <Hg|C3Ph−Si> junctions; a considerably larger increase occurred in the former sample, which has less oxygen content than that of the latter junction (based on the O 1s(O−Si)/Si 2p peak area ratios). These results suggest that the slow oxidation of molecularly modified silicon may, in fact, dictate the electrical performance of the thus formed molecular diode junctions.

Barrier height distribution and dipolar relaxation in metal-insulator-semiconductor junctions with molecular insulator: Ageing effects

“…The physical origin of interface potential fluctuations may arise from some inhomogeneous distribution of dipoles, charge transfer, or charged defects; 76 in molecular junctions, interface oxidation decreases the barrier height at the semiconductor interface, as reported in previous works. 26,49 A. Interface oxidation As shown previously, 24,44,49 the oxidation kinetics of the C 12 H 25 -n Si interface is slow, with a 2 months typical time scale, in contrast with a few hours time scale for the oxidation of hydrogenated Si(111):H surfaces. It is thus expected that ageing at the ambient for 18 months should produce a strongly oxidized C 12 H 25 -n Si interface.…”

“…1) is expected at specific areas with either lower molecular coverage or higher molecular disorder; hence, physically adsorbed oxygen-containing species can be trapped within the organic film or bound to the pinholes. 49 As a consequence, a large dispersion in electrical properties of the corresponding devices is expected and has been observed. 19,[35][36][37] In the particular case of macroscopic a)…”

“…28,32,34,[38][39][40][41][42] Linear saturated (n-alkyl) chains play the role of a nanometer-thick tunnel barrier (TB); however steric molecular constraints do not allow a full passivation of Si(111) surface sites, which remain subject to post-grafting oxidation at the ambient. [43][44][45][46][47][48][49] Substrate oxidation due to oxygen molecule penetration through the OML occurs at increasing rates with decreasing chain length, indicating increasingly poor organization or porosity of the alkyl chains layer. 12 Preferential post-grafting oxidation (Fig.…”

Diamond/β-SiC Composite Thin Films: Preparation, Properties and Applications

“…However, while fabricating thin film based biosensors, the surfaces are more than often chemically or physically treated to make them clean and highly active [36][37][38], aiming at enhancing the adhesion of the chemical or biochemical species on the solid surface while minimizing the nonspecific adsorption of those species which disturbs the sensing process [39,40]. In this context, the wettability of the thin film surface is important to explain its interactions with chemicals or biological species.…”

Palladium-Catalyzed Coupling Reactions for the Functionalization of Si Surfaces: Superior Stability of Alkenyl Monolayers

“…Si-O-C. A weak C-O peak is also present in the Br-PA spectra, which may be due to adsorbed solvent molecules (THF) incorporated into the functionalization layer or the presence of adventitious hydrocarbons. 46 Successful Suzuki coupling is also indicated in figure 3 (c) and…”