Research

Our research is aimed at developing semiconductor-based nanostructures, investigating their fundamental properties and developing a variety of electronic, optoelectronic and photonic devices that are based on these nanostructures. To this end, we have developed several techniques to fabricate silicon based nanostructures (such as porous silicon, silicon nanocrystals (Fig.1a) and silicon photonic crystals (Fig.1b). We have conducted an extensive research to reveal the underlying physical mechanism responsible to the unique optical properties of these nanostructures, particularly the strong, room-temperature luminescence across the visible and the near infrared range of the optical spectrum from most type of silicon nanostructures (inset to Fig.1a). In addition, we have performed an extensive research for exploring transport and conduction phenomena in these nanostructures.

Figure 1: (a) Cross-section TEM image of a superlattice of silicon nanocrystals. The inset shows the red photoluminescence (PL) from the sample. (b) Schematics of a self-reporting silicon-based photonic crystal structure that can detect and quantify E. Coli bacteria in real-time (c) SEM image of silicon nanotubes loaded with nanorods of perovskites (d) SEM image of a laser-based copper printing of a logo for the “Small” journal on an epoxy glass laminate. The width of the printed letters is 50 μm and the letters are gradually printed to a higher height (inside front page cover of the "Small" journal; September 2015)

On the applications side, we have developed methods to fabricate 2D and 3D porous silicon photonic crystals made of periodic silicon structures. We have developed a novel class of photonic biosensors for sensing living cells and bacteria. We have demonstrated a sensitivity of few E. Coli cells per milliliter of solution using the method of RIFTS (reflective interference Fourier transform spectroscopy).

In another research project (in a close collaboration with our industrial partners from PrintLogic Ltd.), we have developed a laser-based method for direct digital printing of metals and metal alloys. The method, called "LIFT" (laser induced forward transfer), is capable of printing complex structures of metals in three-dimensions (3D) with a fairly high spatial resolution; see Fig.1(d). Recently we have extended the capabilities of this technique for direct printing of semiconductors (such as silicon) as well as perovskites. Few printing results are shown in Fig. 1(d).

In another research project, we have developed a novel class of silicon nanotubes (SiNTs), which have been used as a templet for growing small nanorods of metal-halide perovskites. This project, which is conducted in a close collaboration with Prof. Jeff Coffer from TCU, Texas and Prof. Lioz Etgar from the institute of Chemistry, is aimed at developing a novel class of photovoltaic solar cells, particularly hybrid (silicon-perovskites) solar cells. In addition, we investigate the possibility of utilizing the LIFT technique for developing solar cells made of thin films of silicon and perovskites.

Specific research topics related to Nanoscience and Nanotechnology:

Synthesis and Fabrication of semiconductor based nanostructures: including periodic arrays of silicon nanocrystals, silicon nanowires and periodic structures of porous silicon. Developing advance, laser-based, methods for printing, and controlling the shape and the electronic properties of silicon and metal nanostructures.

Structural, optical and electronic properties of semiconductor nanostructures: including electronic microscopy, photoluminescence (PL), time-resolved PL spectroscopy, Cathodoluminescence (CL) spectroscopy and imaging for investigating the optical properties of individual nanostructures. Transport and conduction in systems containing silicon nanostructures.

Towards Applications: Photovoltaic solar cells made of thin films of silicon and organic-inorganic perovskite nanostructures; hybrid structures of perovskite and porous silicon for solar cell applications; thin films of MOS-like transistors and light emitting devices based on silicon nanostructures. Developing biosensors based on silicon photonic crystals; Laser-based printing of silicon and silicon based nanostructures.