Parallel p–n Junctions across Nanowires by One-Step Ex Situ Doping

Abstract

The bottom-up synthesis of nanoscale building blocks is a versatile approach for the formation of a vast array of materials with controlled structures and compositions. This approach is one of the main driving forces for the immense progress in materials science and nanotechnology witnessed over the past few decades. Despite the overwhelming advances in the bottom-up synthesis of nanoscale building blocks and the fine control of accessible compositions and structures, certain aspects are still lacking. In particular, the transformation of symmetric nanostructures to asymmetric nanostructures by highly controlled processes while preserving the modified structural orientation still poses a significant challenge. We present a one-step ex situ doping process for the transformation of undoped silicon nanowires (i-Si NWs) to p-type/n-type (p-n) parallel p-n junction configuration across NWs. The vertical p-n junctions were measured by scanning tunneling microscopy (STM) in concert with scanning tunneling spectroscopy (STS), termed STM/S, to obtain the spatial electronic properties of the junction formed across the NWs. Additionally, the parallel p-n junction configuration was characterized by off-axis electron holography in a transmission electron microscope to provide an independent verification of junction formation. The doping process was simulated to elucidate the doping mechanisms involved in the one-step p-i-n junction formation.

Boron Monolayer Doping: Role of Oxide Capping Layer, Molecular Fragmentation, and Doping Uniformity at the Nanoscale

“…To date, most reports focus on studying the influence of surface chemistry used, molecular footprint, and details of capping layer used on the resulting doping levels. [ 18,27–32 ] The application of phenylboronic acid (PBA) monolayers in doping was previously studied, in part, for the formation of sharp p–i–n junctions in SiNWs, [ 17 ] for studying dopant diffusion and activation in SiNWs, [ 33 ] and for dopant patterning. [ 34 ] Herein, a systematic study to understand the impact of oxide cap deposition on the B‐doping by PBA monolayer is presented.…”

Functionalization of Silica Nanoparticles and Native Silicon Oxide with Tailored Boron-Molecular Precursors for Efficient and Predictive p-Doping of Silicon

“…To circumvent this capping issue, the monolayer contact doping (MLCD) concept was recently proposed. 17,18 While providing good results in the formation of (ultra)shallow junctions, the use of two substrates (donor and acceptor) makes this ex situ technique not as straightforward as approaches related to MLD, relying on only one substrate.In this work, we show how to avoid these issues by the use of a simple bottom-up methodology based on the grafting of tailored boron-containing molecular precursors (anchoring/ self-protected) on the thin layer of native silica present on top of silicon wafers. This method takes advantage of (i) the presence of a tunable coverage/density of silanols on silica as…”

Monolayer functionalization of silicon micro and nanowires : towards solar-to-fuel and sensing devices

“…The technique was also used to create parallel p-i-n junctions inside nanowires. 97 Here, Hazut et al applied MLCD to undoped nanowires by sandwiching the nanowires between two dummy substrates, including one boroncontaining (phenylboronic acid) and one phosphorus-containing (tetraethyl methylenediphosphonate) donor substrate. The junction formation was confirmed by scanning tunneling microscopy measurements in combination with scanning tunneling spectroscopy.…”

“…Blue excitation (λ ex = 490-510 nm) and green emission (λ em = 520-550 nm) were filtered using a Chroma filter cube. 97 …”