Silicon-pyrene/perylene hybrids as molecular rectifiers

Abstract

We have synthesized two alkenyl (C-6 and C-11 chains) pyrenes and one alkenyl (C-11 chain) perylene as the σ-π systems, which were electro-grafted on H-terminated Si surfaces to form the respective monolayers. The I-V characteristics of the monolayers revealed pronounced rectification in forward bias with a maximum rectification ratio (RR) of 2.5 × 10(5) at 2.5 V for the C-6-pyrene 4b, 1000 at 1.5 V for the C-11-pyrene 4a and 3000-5000 at 1.75 V for the C-11-perylene 3. The higher RR of the devices containing 4b compared to those of 4a and 3 is possibly due to better alignment and packing of the 4b-monolayers on the Si substrate. The rectification was explained using the ab initio molecular-orbital calculations.

Fluorinated benzalkylsilane molecular rectifiers

“…These values are on par with some of the highest reported in the literature, with a thiophene-1,1-dioxide oligomer exhibiting an R of ~200, a ferrocene-alkanethiolate with an R = 150, and ferrocene placed on a monolayer of β-cyclodextrin demonstrating an R of 170153343. We note, however, that larger values can also be obtained4445. Nevertheless, our molecules have the additional advantage of being very low-cost since the precursors are common organic molecules, being easy to synthesize, and requiring minimal purification steps.…”

A novel design for porphyrin based D–s–A systems as molecular rectifiers

“…These showed marginal rectifications with RR I + /I – values of 0.75 and 2, respectively. Recently, we constructed a n + -Si/pyrene C-11 monolayers/Hg device, which exhibited current rectification in the positive bias with RR of 100 at 1 V. 53 Furthermore, a n + -Si/5-(4-undecenyloxyphenyl)-10,15,20-triphenyl porphyrin (TPP C-11) monolayers/Hg system constructed by our group showed a marginally asymmetric I–V with significant hysteresis. In the positive bias scan (0 to +0.8 V), the current jumped by an order of magnitude at +0.6 V. However, on the reverse scan (+0.8 to 0 V) the current did not retrace the curve and remained at a higher value.…”

“…In particular, the RR values of the Hg/ 5b /Si (n++) devices were far superior to that of molecular rectifiers reported so far. 53 , 57 , 58 …”

“…To the best of our knowledge, such high RR values are rare, except for previous devices constructed by C. A. Nijhuis and Whitesides's group, 51 , 57 , 58 L. Venkataraman 52 and a recent publication from our own group. 53 The monolayer with the C-11 linker was more compact and showed a 10 5 times high rectification ratio (RR) relative to the other similar system having the C-6 linker, possibly because of the compact packing. The rectification mechanism was explained on the basis of Aviram and Ratner’s theory of rectification by using ab initio molecular orbital calculations.…”

Rapid Surface Functionalization of Hydrogen-Terminated Silicon by Alkyl Silanols

“…1−3 Among all substrates, silicon surfaces are of utmost interest because of its unique optoelectronic properties, 4−6 which provide applications in biosensing, 7,8 molecular electronics 9,10 and solar cell devices. 11−13 In this regard, the nature of the grafting to the silicon surface is a critical issue for electronic applications, as the chemical identity of this linkage can have significant effects on the electronics of the underlying semiconductor.…”