Coherent Diffraction Imaging of Single 95nm Nanowires

Photonic or electronic confinement effects in nanostructures become significant when one of their dimension is in the 5-300 nm range. Improving their development requires the ability to study their structure - shape, strain field, interdiffusion maps - using novel techniques. We have used coherent diffraction imaging to record the 3-dimensionnal scattered intensity of single silicon nanowires with a lateral size smaller than 100 nm. We show that this intensity can be used to recover the hexagonal shape of the nanowire with a 28nm resolution. The article also discusses limits of the method in terms of radiation damage.Comment: 5 pages, 5 figure

PtSi Clustering In Silicon Probed by Transport Spectroscopy

Metal silicides formed by means of thermal annealing processes are employed as contact materials in microelectronics. Control of the structure of silicide/silicon interfaces becomes a critical issue when the device characteristic size is reduced below a few tens of nanometers. Here we report on silicide clustering occurring within the channel of PtSi/Si/PtSi Schottky barrier transistors. This phenomenon is investigated through atomistic simulations and low-temperature resonant tunneling spectroscopy. Our results provide evidence for the segregation of a PtSi cluster with a diameter of a few nanometers from the silicide contact. The cluster acts as metallic quantum dot giving rise to distinct signatures of quantum transport through its discrete energy states

An integrated cryogenic optical modulator

Integrated electrical and photonic circuits (PIC) operating at cryogenic temperatures are fundamental building blocks required to achieve scalable quantum computing, and cryogenic computing technologies. Optical interconnects offer better performance and thermal insulation than electrical wires and are imperative for true quantum communication. Silicon PICs have matured for room temperature applications but their cryogenic performance is limited by the absence of efficient low temperature electro-optic (EO) modulation. While detectors and lasers perform better at low temperature, cryogenic optical switching remains an unsolved challenge. Here we demonstrate EO switching and modulation from room temperature down to 4 K by using the Pockels effect in integrated barium titanate (BaTiO3)-based devices. We report the nonlinear optical (NLO) properties of BaTiO3 in a temperature range which has previously not been explored, showing an effective Pockels coefficient of 200 pm/V at 4 K. We demonstrate the largest EO bandwidth (30 GHz) of any cryogenic switch to date, ultra-low-power tuning which is 10^9 times more efficient than thermal tuning, and high-speed data modulation at 20 Gbps. Our results demonstrate a missing component for cryogenic PICs. It removes major roadblocks for the realisation of novel cryogenic-compatible systems in the field of quantum computing and supercomputing, and for interfacing those systems with the real world at room-temperature

Joule-assisted silicidation for short-channel silicon nanowire devices

We report on a technique enabling electrical control of the contact silicidation process in silicon nanowire devices. Undoped silicon nanowires were contacted by pairs of nickel electrodes and each contact was selectively silicided by means of the Joule effect. By a realtime monitoring of the nanowire electrical resistance during the contact silicidation process we were able to fabricate nickel-silicide/silicon/nickel- silicide devices with controlled silicon channel length down to 8 nm.Comment: 6 pages, 4 figure

Multifunctional Devices and Logic Gates With Undoped Silicon Nanowires

We report on the electronic transport properties of multiple-gate devices fabricated from undoped silicon nanowires. Understanding and control of the relevant transport mechanisms was achieved by means of local electrostatic gating and temperature dependent measurements. The roles of the source/drain contacts and of the silicon channel could be independently evaluated and tuned. Wrap gates surrounding the silicide-silicon contact interfaces were proved to be effective in inducing a full suppression of the contact Schottky barriers, thereby enabling carrier injection down to liquid-helium temperature. By independently tuning the effective Schottky barrier heights, a variety of reconfigurable device functionalities could be obtained. In particular, the same nanowire device could be configured to work as a Schottky barrier transistor, a Schottky diode or a p-n diode with tunable polarities. This versatility was eventually exploited to realize a NAND logic gate with gain well above one.Comment: 6 pages, 5 figure

Reversible Al Propagation in Si x Ge 1-x Nanowires

While reversibility is a fundamental concept in thermodynamics, most reactions are not readily reversible, especially in solid state physics. For example, thermal diffusion is a widely known concept, used among others to inject dopant atoms into the substitutional positions in the matrix and improve the device properties. Typically, such a diffusion process will create a concentration gradient extending over increasingly large regions, without possibility to reverse this effect. On the other hand, while the bottom up growth of semiconducting nanowires is interesting, it can still be difficult to fabricate axial heterostructures with high control. In this paper, we report a reversible thermal diffusion process occurring in the solid-state exchange reaction between an Al metal pad and a SixGe1-x alloy nanowire observed by in-situ transmission electron microscopy. The thermally assisted reaction results in the creation of a Si-rich region sandwiched between the reacted Al and unreacted SixGe1-x part, forming an axial Al/Si/SixGe1-x heterostructure. Upon heating or (slow) cooling, the Al metal can repeatably move in and out of the SixGe1-x alloy nanowire while maintaining the rod-like geometry and crystallinity, allowing to fabricate and contact nanowire heterostructures in a reversible way in a single process step, compatible with current Si based technology. This interesting system is promising for various applications, such as phase change memories in an all crystalline system with integrated contacts, as well as Si/SixGe1-x/Si heterostructures for near-infrared sensing applications

SiNWs-based electrochemical double layer micro-supercapacitors with wide voltage window (4V) and long cycling stability using a protic ionic liquid electrolyte

The present work reports the use and application of a novel protic ionic liquid (triethylammonium bis(tri fluoromethylsulfonyl)imide; NEtH TFSI) as an electrolyte for symmetric planar micro-supercapacitors based on silicon nanowire electrodes. The excellent performance of the device has been successfully demonstrated using cyclic voltammetry, galvanostatic charge-discharge cycles and electrochemical impedance spectroscopy. The electrochemical characterization of this system exhibits a wide operative voltage of 4 V as well as an outstanding long cycling stability after millions of galvanostatic cycles at a high current density of 2 mA cm. In addition, the electrochemical double layer micro-supercapacitor was able to deliver a high power density of 4 mWcm in a very short time pulses (a few ms). Our results could be of interest to develop prospective on-chip micro-supercapacitors using protic ionic liquids as electrolytes with high performance in terms of power and energy densities