Near-Infrared Schottky Silicon Photodetectors Based on Two Dimensional Materials

Since its discovery in 2004, graphene has attracted the interest of the scientific community due to its excellent properties of high carrier mobility, flexibility, strong light-matter interaction and broadband absorption. Despite of its weak light optical absorption and zero band gap, graphene has demonstrated impressive results as active material for optoelectronic devices. This success pushed towards the investigation of new two-dimensional (2D) materials to be employed in a next generation of optoelectronic devices with particular reference to the photodetectors. Indeed, most of 2D materials can be transferred on many substrates, including silicon, opening the path to the development of Schottky junctions to be used for the infrared detection. Although Schottky near-infrared silicon photodetectors based on metals are not a new concept in literature the employment of two-dimensional materials instead of metals is relatively new and it is leading to silicon-based photodetectors with unprecedented performance in the infrared regime. This chapter aims, first to elucidate the physical effect and the working principles of these devices, then to describe the main structures reported in literature, finally to discuss the most significant results obtained in recent years

Bioconjugation of a PNA Probe to Zinc Oxide Nanowires for Label-Free Sensing

Zinc oxide nanowires (ZnONWs) are largely used in biosensing applications due to their large specific surface area, photoluminescence emission and electron mobility. In this work, the surfaces of ZnONWs are modified by covalent bioconjugation of a peptidic nucleic acid (PNA) probe whose sequence is properly chosen to recognize a complementary DNA (cDNA) strand corresponding to a tract of the CD5 mRNA, the main prognostic marker of chronic lymphatic leukemia. The interaction between PNA and cDNA is preliminarily investigated in solution by circular dichroism, CD melting, and polyacrylamide gel electrophoresis. After the immobilization of the PNA probe on the ZnONW surface, we demonstrate the ability of the PNA-functionalized ZnONW platform to detect cDNA in the μM range of concentration by electrical, label-free measurements. The specificity of the sensor is also verified against a non-complementary DNA sequence. These preliminary results highlight the potential application of PNA-bioconjugated ZnONWs to label-free biosensing of tumor markers

CMOS-compatible amorphous silicon photonic layer integrated with VLSI electronics

Hydrogenated amorphous silicon (a-Si:H) is recently emerging as a promising material to provide microchips with passive and active photonic functions through a back-end and CMOS-compatible technological process. In this paper, we discuss the performances achieved with different configurations of a-Si:H-based electro-optical amplitude modulators integrated into passive waveguides. All of the analyzed devices are based on the plasma dispersion effect, a phenomenon that allows to reach useful performances at the communication wavelengths of λ∼1.55 μm. Mixed electro-optic simulations, in both steady state and transient conditions, for optimized active photonic devices are finally presented. © 2014 AEIT

Pyroelectric effect control: Design, fabrication, and characterization of a microheaters array for biomedical applications

An innovative microheater array design is realized on a lithium niobate crystal, to induce a uniform pyroelectric effect on an area of 12.5 × 12.5 mm2. Thermal analyses of the device were performed both experimentally and numerically using a FLIR thermocamera and COMSOLTM Multiphysics. A series of preliminary numerical simulations were carried out to obtain the optimized design of the aforementioned specifications. The microheaters were fabricated on the + Z surface of the lithium niobate crystal using a photolithography process followed by titanium thin-film deposition. We performed on this device a series of electrothermal characterizations; the results of the measurements showed good agreement with the numerical model in terms of heat distribution, accomplishing a comparison between the thermal maps coming from the two methodologie

Near-infrared photodetectors based on embedded graphene

In last years, the introduction of 2-dimensional materials such as graphene has revolutionized the world of silicon photonics. In this work, we demonstrate a new approach for integrating graphene into silicon-based photodetectors. We leverage a thin film of hydrogenated amorphous silicon to embed the graphene within two different photonic structures, an optical Fabry-Pérot microcavity, and a waveguide, achieving a stronger light-matter interaction. The investigated devices have shown promising performance resulting in responsivities as high as 27 mA/W and 0.15 A/W around 1550 nm, respectively

Hybrid Organic/Inorganic Nanomaterials for Biochemical Sensing

In this paper, different nanostructured semiconductors with advanced properties are explored for the realization of both optical and electrical biosensors for DNA detection. A hybrid sensor constituted by graphene oxide (GO) covalently grafted on a porous silicon (PSi) matrix is realized. A peptide nucleic acid (PNA) probe, able to recognize its complementary DNA (c-DNA) sequence, is immobilized on the surface of PSi/GO device for label-free optical sensing. Electrical sensing of DNA is also demonstrated using a Zinc Oxide Nanowires (ZnONWs) sensor functionalized with PNA probe; the I–V characteristic of the device depends on the c-DNA concentration under analysis