Erbium Silicide Growth in the Presence of Residual Oxygen

The chemical changes of Ti/Er/n-Si(100) stacks evaporated in high vacuum and grown ex situ by rapid thermal annealing were scrutinized. The emphasis was laid on the evolution with the annealing temperature of (i) the Er-Si solid-state reaction and (ii) the penetration of oxygen into Ti and its subsequent interaction with Er. For that sake, three categories of specimens were analyzed: as-deposited, annealed at 300{\deg}C, and annealed at 600{\deg}C. It was found that the presence of residual oxygen into the annealing atmosphere resulted in a substantial oxidation of the Er film surface, irrespective of the annealing temperature. However, the part of the Er film in intimate contact with the Si bulk formed a silicide (amorphous at 300{\deg}C and crystalline at 600{\deg}C) invariably free of oxygen, as testified by x-ray photoelectron spectroscopy depth profiling and Schottky barrier height extraction of 0.3 eV at 600{\deg}C. This proves that, even if Er is highly sensitive to oxygen contamination, the formation of low Schottky barrier Er silicide contacts on n-Si is quite robust. Finally, the production of stripped oxygen-free Er silicide was demonstrated after process optimization

Silicon nanostructures and coplanar waveguides for biosensors

The biosensors market had a considerable development in the last decade and is expected to increase at a quick pace in the coming years. The driving force behind this important expansion is a constant need to improve the current methods for environmental monitoring and for rapid pathogen detection. Mainly destined to point-of-care devices, biosensors are spreading through home diagnostics, bio-defense, and food industry. This high demand pushes for the development of new and more precise devices. Two fundamentally different types of sensing devices were built and studied in this work. Both types of devices were engineered using conventional micro- and nano-fabrication techniques in order to allow for a quick integration with electronic circuits. The first type is based on silicon nanowires (SiNWs) and the devices function similarly to field effect transistors. The full manufacturing protocol, which results in nanowires with trapezoidal shape, is carefully described. The effect of surface modification with (3-aminopropyl)triethoxysilane (APTES), on the electrical properties of the devices, was studied. Important changes in the threshold voltage and the subthreshold slope were observed between the as-fabricated devices and the APTES-conditioned ones. Furthermore, we show that the APTES significantly improves the stability of the SiNWs compared with more conventional micro-devices. The detection of proteins was studied with these SiNWs-based sensors. The second type of devices is based on coplanar waveguides and their functioning resembles that of capacitive sensors. These devices sense the change in the dielectric properties of the surrounding media and their use for the dielectric characterization of various materials is presented first. Subsequently, we employed these devices, operating in the radio-frequency range, in conjunction with gravitational sedimentation to develop a novel colloid-based biosensing method. This technique, in which the settling of bio-functionalized polystyrene beads clusters is monitored, was applied to the detection of proteins.(FSA - Sciences de l'ingénieur) -- UCL, 201

Self-formation of sub-10 nm nanogaps based on silicidation

We have developed a simple and reliable method for the fabrication of sub-10 nm wide nanogaps. The self-formed nanogap is based on the stoichiometric solid-state reaction between metal and silicon atoms during the silicidation process. The nanogap width is determined by the metal layer thickness. Our proposed method can produce symmetric and asymmetric electrode nanogaps, as well as multiple nanogaps within one unique process step, for potential application to biological/chemical sensors and nanoelectronics, such as resistive switches, storage devices, and vacuum channel transistors. This method provides high throughput and it is suitable for large-scale production

Vertical single nanowire devices based on conducting polymers.

A simple scheme for single conducting polymer nanowire fabrication and device integration is presented. We discuss a combined top-down and bottom-up approach for the sequential, precise manufacture of vertical polyaniline nanowires. The method is scalable and can be applied on rigid as well as on flexible substrates. The kinetics of the template-confined growth is presented and discussed. We further study the electrical behavior of single vertical polyaniline nanowires and address the fabrication of crossbar latches using a criss-cross arrangement of electrodes. The as-synthesized polyaniline nanowires display electric conductivities reaching values as high as 0.4 S cm−1

Tuning the surface conditioning of trapezoidally shaped silicon nanowires by (3-aminopropyl)triethoxysilane.

We report on the electrical performance of silane-treated silicon nanowires configured as n + – p – n + field effect transistors. The functionalization of the silicon oxide shell with (3-aminopropyl)triethoxysilane controls the formation of the conduction channel in the trapezoidal cross-section nanowires. By carefully adjusting the surface conditioning protocol, robust electrical characteristics were achieved in terms of device-to-device reproducibility for the studied silicon nanowire transistors: the standard deviation displays a fourfold decrease for the threshold voltage together with a sevenfold improvement for the subthreshold slope

Mathematics, statistics and single element resolution/processing in nanoporous templates.

Nanoporous materials and templates have definitely settled the concept ofmass production of low dimensional structures. The major drawback that restricts their pervasive integration into real working devices is the mismatch between their dimensionality and today’s technological ability. For example, the hexagonal lattice is considered unsuitable for orthogonal arrangements required by the industry standard circuits. In this talk, we propose a general solution for the ultimate resolution processing of nanoporous templates. No overlay alignment is required to achieve single nanopore and subsequently nanowire resolution with probabilities as high as 92% upon proper modulation of the pattern mask size

Colloidal self-assembly as a versatile tool for direct writing of three-dimensional silicon-based photonic lattices.

In this talk, the fabrication and characterization of 3D silicon photonic lattices using colloidal sphere nanolithography is presented. Ordered monolayers arrays of polystyrene micro- and nano-particles fabricated using interfacial self-assembly have been explored with respect to that. The hexagonal packing has been mainly employed due to its simplicity and reliability in large area fabrication. The exploration and realization nanospheres square arrangements induced by the shape of the meniscus at the edges of the silicon substrates has been tested as well. The colloidal templates have been either used as such or subsequently modified to fabricate aluminum hard-masks for the deep reactive ion etching of silicon (DRIE). A single-step etch protocol was developed in order to generate periodic diameter modulated self-aligned nanochannels in silicon. The method is based on the standard Bosch silicon DRIE protocol with subsequent improvements in order to precisely design and adjust the period and the size of the etch modulations. The principle relies on consecutive surface passivation and etch steps using C4F8 and SF6 plasma chemistries respectively. The diffusion of fresh reacting and etch product species into the etched channels was found to play an important role affecting the structural uniformity of the fabricated structures. The diffusion induced etch rate drift was corrected by adjusting the reaction times. The optimized protocols were used to fabricate various 3D nanostructures in silicon. Ordered arrays of diameter modulated post or porous architectures have been successfully realized by adding the third dimension to the 2D colloidal crystal assemblies through the developed DRIE protocol. Delamination of silicon nanostructured stacks or kinked nanowires can be also realized by carefully adjusting the balance between the deposition and etch steps. Finally, we demonstrate the realization of the 3D photonic crystal quality lattices exhibiting optical band-gaps in the infrared spectral region proving the potential of the respective technique for fast, simple and large-scale fabrication of photonic structures [1]