Temperature-dependent photoluminescence of surface-engineered silicon nanocrystals

In this work we report on temperature-dependent photoluminescence measurements (15–300 K), which have allowed probing radiative transitions and understanding of the appearance of various transitions. We further demonstrate that transitions associated with oxide in SiNCs show characteristic vibronic peaks that vary with surface characteristics. In particular we study differences and similarities between silicon nanocrystals (SiNCs) derived from porous silicon and SiNCs that were surface-treated using a radio-frequency (RF) microplasma system

Improved Optoelectronic Properties of Silicon Nanocrystals/Polymer Nanocomposites by Microplasma-Induced Liquid Chemistry

We have demonstrated that three-dimensional (3D) surface engineering of silicon nanocrystals (SiNCs) by direct current microplasma processing in water with poly(3,4-ethylenedioxythiophene) doped by poly(styrenesulfonate) (PEDOT:PSS) can lead to nanocomposites with enhanced optoelectronic performance. Specifically, we have successfully shown improved photoluminescence properties of SiNCs inside water-based solution. The results also confirm that SiNCs become stable in water with potential application impact for biorelated applications. We have also shown that the microplasma processing in the presence of the polymer helps prevent the fast oxidation process over a longer period of time in comparison to the unprocessed sample. Furthermore, the assessment of transport properties confirmed the improvement of exciton dissociation after microplasma surface engineering; this can have direct implications for higher performance optoelectronic devices including solar cells.</p

Enhanced UV Emission of GaN Nanowires Functionalized by Wider Band Gap Solution-Processed p-MnO Quantum Dots

International audienc

GaN and InGaN nanowires prepared by metal-assisted electroless etching:experimental and theoretical studies

Abstract We investigate the optical and structural properties of GaN and InGaN nanowires (NWs) fabricated by metal-assisted electroless etching in a hydrofluoric acid (HF) solution. The emission spectra of GaN and InGaN NWs exhibit a red shift compared to the as-grown samples resulting from an increase in the surface-to-volume ratio and stress relaxation in these nanostructures. The carrier lifetimes of GaN and InGaN NWs were measured. In addition, density functional theory (DFT) investigations were carried out on GaN and InGaN NWs using the generalized gradient approximation (GGA), including the Hubbard U parameter. The presence of compressive stress in the NWs was confirmed by the DFT calculations, which indicated that it induces a change in the lattice parameter along the c-direction. Formation energy calculations showed that In is a much more stable dopant in the GaN NWs compared to the native point defects, such as Ga and N vacancies. Moreover, electronic structure analysis revealed that the complex defects formed by the presence of In along with vacancy defects shifts the valence band maximum, thus changing the conducting properties of the NWs

Varying Surface Chemistries for p‑Doped and n‑Doped Silicon Nanocrystals and Impact on Photovoltaic Devices

Doping of quantum confined nanocrystals offers unique opportunities to control the bandgap and the Fermi energy level. In this contribution, boron-doped (p-doped) and phosphorus-doped (n-doped) quantum confined silicon nanocrystals (SiNCs) are surface-engineered in ethanol by an atmospheric pressure radio frequency microplasma. We reveal that surface chemistries induced on the nanocrystals strongly depend on the type of dopants and result in considerable diverse optoelectronic properties (e.g., photoluminescence quantum yield is enhanced more than 6 times for n-type SiNCs). Changes in the position of the SiNCs Fermi levels are also studied and implications for photovoltaic application are discussed

Impact of silicon nanocrystal oxidation on the nonmetallic growth of carbon nanotubes

Carbon nanotube (CNT) growth has been demonstrated recently using a number of nonmetallic semiconducting and metal oxide nanoparticles, opening up pathways for direct CNT synthesis from a number of more desirable templates without the need for metallic catalysts. However, CNT growth mechanisms using these nonconventional catalysts has been shown to largely differ and reamins a challenging synthesis route. In this contribution we show CNT growth from partially oxidized silicon nanocrystals (Si NCs) that exhibit quantum confinement effects using a microwave plasma enhanced chemical vapor deposition (PECVD) method. On the basis of solvent and a postsynthesis frgamentation process, we show that oxidation of our Si NCs can be easily controlled. We determine experimentally and explain with theoretical simulations that the Si NCs morphology together with a necessary shell oxide of ∼1 nm is vital to allow for the nonmetallic growth of CNTs. On the basis of chemical analysis post-CNT-growth, we give insight into possible mechanisms for CNT nucleation and growth from our partially oxidized Si NCs. This contribution is of significant importance to the improvement of nonmetallic catalysts for CNT growth and the development of Si NC/CNT interfaces

Three-dimensional band diagram in lateral polarity junction III-nitride heterostructures

Three-dimensional band diagram in lateral polarity junction III-nitride heterostructure