Molecular Passivation of Mercury−Silicon (p-type) Diode Junctions:  Alkylation, Oxidation, and Alkylsilation

Abstract

To evaluate the electrical performance of molecularly modified metal-semiconductor diode junctions, organic monolayers were grafted on both hydrogen-terminated and oxidized silicon (p-type) surfaces. Three model systems, i.e., Hg|C 12 H 25 -Si, Hg|SiO 2 -Si, and Hg|C 12 H 25 SiO 3 -SiO 2 -Si, were prepared and systematically characterized based on their current-voltage and capacitance-voltage properties. The experimental results showed that mercury-silicon junctions modified with n-dodecyl monolayer display better rectifying behavior, i.e., larger rectifying ratio and smaller empirical ideality factor (i.e., close to unity), than those passivated with SiO 2 thin films and n-dodecylsiloxane monolayers (formed on oxidized silicon). The differential capacitance measurements revealed that organic modified junctions (both alkylated and alkylsilated samples) have substantially lower densities of interface states in comparison with that of Hg|SiO 2 -Si. This work provides a clear assessment of the varied device performance among differently prepared metal-moleculesemiconductor junctions, which is complementary to the topic studies on the electron transport across these molecular interfaces. More importantly, the present research augments the potential applications of molecular modification and surface engineering in the fabrication of silicon-based microelectronic devices.

Molecules on Si: Electronics with Chemistry

“…The analysis of interface states of complete junctions can be done with frequency-noise analysis [73] or forward bias capacitance. [66] Both indicate the presence of interface states in alkyl MOMS, and a decrease in their density after direct alkyl CÀSi binding, compared to native (piranha) SiO 2 , down to 10 11 -10 12 eV À1 cm À2 . [44,65,66,74] 4.…”

“…[66] Both indicate the presence of interface states in alkyl MOMS, and a decrease in their density after direct alkyl CÀSi binding, compared to native (piranha) SiO 2 , down to 10 11 -10 12 eV À1 cm À2 . [44,65,66,74] 4. Transport across Si/Molecules/Metal Junctions ME is commonly concerned with electronic transport across molecules.…”

“…[44,66] Transport across very short alkyl monolayers, directly bound to Si, and characterized by spectroscopy, [33,67] was studied with Hg, [19] Au [2] and other metals as second contact. [68] In other work powerful techniques for characterizing Si MOMS were used and, in part, adapted.…”

Temperature dependence of current density and admittance in metal-insulator-semiconductor junctions with molecular insulator

“…4 Covalently bound linear saturated (n-alkyl) chains form robust molecular layers with a high coverage and 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. [5][6][7] Electrical transport properties of hybrid M-OML-SC devices have been widely studied [8][9][10][11][12][13][14][15][16][17][18][19] due to their relatively low density of electrically active defects at the OML-Si interface. [20][21][22][23] Analysis of current-voltage (I-V) characteristics of molecular MIS tunnel junctions (M-OML-SC) is still a controversial topic due to the simultaneous contribution of different mechanisms (tunneling, thermionic emission (TE), and generation-recombination) potentially involved in the transport of electrical charge carriers, in addition to some influence of series resistance at high current density.…”

“…[20][21][22][23] Analysis of current-voltage (I-V) characteristics of molecular MIS tunnel junctions (M-OML-SC) is still a controversial topic due to the simultaneous contribution of different mechanisms (tunneling, thermionic emission (TE), and generation-recombination) potentially involved in the transport of electrical charge carriers, in addition to some influence of series resistance at high current density. Several methods were proposed to analyze the direct current (dc) transport properties, [8][9][10][11][12][13][14][15][16][17][18][19] however, most studies were performed only at room temperature. In spite of some efforts to combine tunneling and thermionic emission transport through weighting parameters with little physical basis, 14,15 there is no clear method to evaluate the contribution of a thin (d T ¼ 1À2 nm) molecular tunnel barrier in the regime where both mechanisms contribute to the current.…”