Abstract
Silicon nanowires inspire since decades a great interest for their fundamental scientific importance and their potential in new technologies. When decorated with organic molecules they form hybrid composites with applications in various fields, from sensors to life science. Specifically the diethyl 1-propylphosphonate/Si combination is considered as a promising alternative to the conventional semiconductor n-type doping methods, thanks to its solution-based processing, which is damage-free and intrinsically conformal. For these characteristics, it is a valid doping process for patterned materials and nanostructures such as the nanowires. Our joined experimental and theoretical study provides insights at atomistic level on the molecular activation, grafting and self-assembling mechanisms during the deposition process. For the first time to the best of our knowledge, by using scanning transmission electron microscopy the direct visualization of the single molecules arranged over the Si nanowire surface is reported. The results demonstrate that the molecules undergo to a sequential decomposition and self-assembling mechanism, finally forming a chemical bond with the silicon atoms. The ability to prepare well-defined molecule decorated Si nanowires opens up new opportunities for fundamental studies and nanodevice applications in diverse fields like physics, chemistry, engineering and life sciences.
Highlights
Several decades after their introduction Si nanowires (SiNWs) still represent the subject of a vast literature, reaching a publication record of more than 1500 papers per year
The organic molecule diethyl 1-propylphosphonate (DPP) is used as dopant vector and presents the additional property to release, upon high temperature annealing, phosphorous atoms which subsequently diffuse from the surface towards the Si bulk, where they work as dopants[17]
After the deposition of the DPP molecules, the SiNWs were collected on a Transmission Electron Microscopy (TEM) grid and analyzed
Summary
Several decades after their introduction Si nanowires (SiNWs) still represent the subject of a vast literature, reaching a publication record of more than 1500 papers per year (http://wcs.webofknowledge.com). When the SiNWs surface is functionalized with organic molecules, it forms a hybrid nanosystem exhibiting other properties and functionalities such as surface passivation and tunable wettability[7] This hybrid structure finds exciting application in life sciences, where it has been proposed as next-generation therapeutic devices, as analytical tool to decipher how neurons store and process information, or for recording intracellular bioelectrical signals to understand the cells and cell-networks behavior in neural and cardiac systems[8,9,10,11,12,13,14]. There is still no detailed and in-depth information on how the molecule is bound and on its high-resolution visualization
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