Tandem solar cells consisting of amorphous and microcrystalline silicon junctions with the top junction nanopatterned as a two-dimensional photonic crystal are studied. Broadband light trapping, detailed electron/hole transport, and photocurrent matching modulation are considered. It is found that the absorptances of both junctions can be significantly increased by properly engineering the duty...

A plethora of work has been dedicated to the analysis of cell behavior on substrates with ordered topographical features. However, the natural cell microenvironment is characterized by biomechanical cues organized over multiple scales. Here, randomly rough, self-affinefractal surfaces are generated out of silicon,where roughness Ra and fractal dimension Df are independently controlled. The prol...

Using angle-resolved photoelectron spectroscopy we investigate the electronic valence band structure of the Si(331)-(12 × 1) surface reconstruction for which we recently proposed a structural model containing silicon pentamers as elementary structural building blocks. We find that this surface, reported to be metallic in a previous study, shows a clear band gap at the Fermi energy, indicating s...

Nanowire lithography (NWL) uses nanowires (NWs), grown and assembled by chemical methods, as etch masks to transfer their one-dimensional morphology to an underlying substrate. Here, we show that SiO2 NWs are a simple and compatible system to implement NWL on crystalline silicon and fabricate a wide range of architectures and devices. Planar field-effect transistors made of a single SOI-NW chan...

We demonstrate record performance of series-coupled silicon racetrack resonators exhibiting the Vernier effect. Our device has an interstitial peak suppression (IPS) of 25.5 dB, which is 14.5 dB larger than previously reported results. We also demonstrate the relationship between the inter-ring gap distance and the IPS as well as the 3 dB bandwidth (BW) both theoretically and experimentally. Na...

We demonstrate experimentally ultrafast all-optical switching in subwavelength nonlinear dielectric nanostructures exhibiting localized magnetic Mie resonances. We employ amorphous silicon nanodisks to achieve strong self-modulation of femtosecond pulses with a depth of 60% at picojoule-per-disk pump energies. In the pump-probe measurements, we reveal that switching in the nanodisks can be gove...

By manipulating the interfacial interactions between the peptide templates and the silicate species derived from TEOS and APTES, a facile biomimetic method was developed for the fabrication of silica nanostructures exhibiting "string-of-beads" and fibrillar morphologies of varied sizes.

We show the application of a commercially available photopatternable silicone (PPS) that combines the advantageous features of both PDMS and SU-8 to address a critical bioMEMS materials deficiency. Using PPS, we demonstrate the ability to pattern free-standing mechanically isolated elastomeric structures on a silicon substrate: a feat that is challenging to accomplish using soft lithography-bas...