Photoresistance switching of plasmonic nanopores.

Fast and reversible modulation of ion flow through nanosized apertures is important for many nanofluidic applications, including sensing and separation systems. Here, we present the first demonstration of a reversible plasmon-controlled nanofluidic valve. We show that plasmonic nanopores (solid-state nanopores integrated with metal nanocavities) can be used as a fluidic switch upon optical excitation. We systematically investigate the effects of laser illumination of single plasmonic nanopores and experimentally demonstrate photoresistance switching where fluidic transport and ion flow are switched on or off. This is manifested as a large (∼ 1-2 orders of magnitude) increase in the ionic nanopore resistance and an accompanying current rectification upon illumination at high laser powers (tens of milliwatts). At lower laser powers, the resistance decreases monotonically with increasing power, followed by an abrupt transition to high resistances at a certain threshold power. A similar rapid transition, although at a lower threshold power, is observed when the power is instead swept from high to low power. This hysteretic behavior is found to be dependent on the rate of the power sweep. The photoresistance switching effect is attributed to plasmon-induced formation and growth of nanobubbles that reversibly block the ionic current through the nanopore from one side of the membrane. This explanation is corroborated by finite-element simulations of a nanobubble in the nanopore that show the switching and the rectification.

Harnessing plasmon-induced ionic noise in metallic nanopores.

The ionic properties of a metal-coated silicon nanopore were examined in a nanofluidic system. We observed a strong increase of the ionic noise upon laser light illumination. The effect appeared to be strongly mediated by the resonant excitation of surface plasmons in the nanopore as was demonstrated by means of ionic mapping of the plasmonic electromagnetic field. Evidence from both simulations and experiments ruled out plasmonic heating as the main source of the noise, and point toward photoinduced electrochemical catalysis at the semiconductor-electrolyte interface. This ionic mapping technique described is opening up new opportunities on noninvasive applications ranging from biosensing to energy conversion.

Measuring the electrical resistivity and contact resistance of vertical carbon nanotube bundles for application as interconnects.

Carbon nanotubes (CNT) are known to be materials with potential for manufacturing sub-20 nm high aspect ratio vertical interconnects in future microchips. In order to be successful with respect to contending against established tungsten or copper based interconnects, though, CNT must fulfil their promise of also providing low electrical resistance in integrated structures using scalable integration processes fully compatible with silicon technology. Hence, carefully engineered growth and integration solutions are required before we can fully exploit their potentialities. This work tackles the problem of optimizing a CNT integration process from the electrical perspective. The technique of measuring the CNT resistance as a function of the CNT length is here extended to CNT integrated in vertical contacts. This allows extracting the linear resistivity and the contact resistance of the CNT, two parameters to our knowledge never reported separately for vertical CNT contacts and which are of utmost importance, as they respectively measure the quality of the CNT and that of their metal contacts. The technique proposed allows electrically distinguishing the impact of each processing step individually on the CNT resistivity and the CNT contact resistance. Hence it constitutes a powerful technique for optimizing the process and developing CNT contacts of superior quality. This can be of relevant technological importance not only for interconnects but also for all those applications that rely on the electrical properties of CNT grown with a catalytic chemical vapor deposition method at low temperature.

Growth and characterization of horizontally suspended CNTs across TiN electrode gaps.

A technique is proposed to grow horizontal carbon nanotubes (CNTs) bridging metal electrodes and to assess their electrical properties. A test structure was utilized that allows for selective electrochemical sidewall catalyst placement. The selectivity of the technique is based on the connection of the desired metal electrodes to the silicon substrate where the potential for electrochemical deposition was applied. Control over the Ni catalyst size (15-30 nm) and density (up to 3 x 10(11) particles cm(-2)) is demonstrated. Horizontal CNTs with controlled diameter and density were obtained by CVD growth perpendicular to the sidewalls of patterned TiN electrode structures. Electrode gaps with spacings from 200 nm up to 5 microm could be bridged by both direct CNT-electrode contact and CNT-CNT entanglement. The TiN-CNT-TiN and TiN-CNT-CNT-TiN bridges were electrically characterized without any further post-growth contacting. Resistance values as low as 40 Omega were measured for the smallest gap spacing and depended mainly on the number and configuration of the CNT bridges. The proposed method could be implemented for CNT-based horizontal interconnections and be a route to make different nanoelectronic devices such as chemical and electromechanical sensors.

Ferroelectric Control of Magnetism in Ultrathin HfO2\Co\Pt Layers.

The recent demonstration of ferroelectricity in ultrathin HfO2 has kickstarted a new wave of research into this material. HfO2 in the orthorhombic phase can be considered the first and only truly nanoscale ferroelectric material that is compatible with silicon-based nanoelectronics applications. In this article, we demonstrate the ferroelectric control of the magnetic properties of cobalt deposited on ultrathin aluminum-doped, atomic layer deposition-grown HfO2 (tHfO2 = 6.5 nm). The ferroelectric effect is shown to control the shape of the magnetic hysteresis, quantified here by the magnetic switching energy. Furthermore, the magnetic properties such as the remanence are modulated by up to 41%. We show that this modulation does not only correlate with the charge accumulation at the interface but also shows an additional component associated with the ferroelectric polarization switching. An in-depth analysis using first order reversal curves shows that the coercive and interaction field distributions of cobalt can be modulated up to, respectively, 5.8% and 10.5% with the ferroelectric polarization reversal.

Asymmetric plasmonic induced ionic noise in metallic nanopores.

We present distinct asymmetric plasmon-induced noise properties of ionic transport observed through gold coated nanopores. We thoroughly investigated the effects of bias voltage and laser illumination. We show that the potential drop across top-coated silicon nanocavity pores can give rise to a large noise asymmetry (∼2-3 orders of magnitude). Varying the bias voltage has an appreciable effect on the noise density spectra, typically in the Lorentzian components. The laser power is found to strongly affect the ionic noise level as well as the voltage threshold for light-induced noise generation. The asymmetric noise phenomenon is attributed to plasmon-induced interfacial reactions which promote light-induced charge fluctuation in the ion flow and allow voltage modulation of photo-induced carriers surmounting over such Schottky junctions. We further compare the ionic noise performances of gold nanocavities containing different material stacks, among which thermal oxide passivation of the silicon successfully mitigates the light-induced noise and is also fully CMOS-compatible. The understanding of the described noise characteristics will help to foster multiple applications using related structures including plasmonic-based sensing or plasmon-induced catalysis such as water splitting or solar energy conversion devices.

Sidewall crystalline orientation effect of post-treatments for a replacement metal gate bulk fin field effect transistor.

The crystalline orientation effect is investigated for post-treatments of a replacement metal gate (RMG) p-type bulk fin field effect transistor (FinFET). After post-deposition annealing (PDA) and SF6 plasma treatment, the hole mobility is improved. From low-frequency noise analysis, reduction of the trap density and noise level is observed in PDA- and SF6-plasma-treated devices. (100) sidewall-oriented FinFETs show a lower noise level because of fewer interface traps compared to (110) sidewall-oriented devices. SF6 plasma affects the interface traps, whereas PDA relatively more affects bulk oxide traps for RMG high-k last FinFET.