Interrogation of Single Asperity Electrical Contacts Using atomic force Microscopy With Application to Nems Logic Switches

Energy consumption by computers and electronics is currently 15% of worldwide energy output, and growing. Aggressive scaling of the fully-electronic transistor, which is the fundamental computational element of these devices, has led to significant and immutable energy losses. Ohmic nanoelectromechanical systems (NEMS) logic switches have been recognized as a potential transistor replacement technology with projected energy savings of one to three orders of magnitude over traditional, fully-electronic transistors. However, the use of conventional, adhesive contact materials (i.e. metals) in NEMS switches electrical contacts leads to permanent device seizure or the formation of insulating tribofilms that inhibits commercialization of this technology. Of critical need is a method to efficiently identify and interrogate low adhesion, chemically stable electrical contact material pairs under conditions and scales relevant to NEMS logic switch contacts. This thesis presents the development of two electrical contact testing methods based on atomic force microscopy (AFM) to interrogate electrical contact materials under contact forces and environments representative of NEMS logic switch operating conditions. AFM was used to mimic the interaction of Pt/Pt NEMS logic switch electrical interfaces for up to two billion contact cycles in laboratory timeframes. Contact resistance before cycling significantly exceeded theoretical predictions for clean Pt/Pt interfaces due to adsorbed contaminant films and increased up to six orders of magnitude due to cycling-induced insulating tribopolymer growth. Sliding of the contact with microscale amplitudes lead to significant recovery of conductivity through displacement of the insulating films. Based on this observation, AFM was then used to investigate the role of load, shear, electrical bias, and environment on the electrical robustness of Pt/nitrogen-incorporated ultrananocrystalline diamond (N-UNCD) and Pt/Pt interfaces. N-UNCD was selected because similar diamond films have demonstrated low adhesion, chemical inertness, and compatibility with NEMS logic device fabrication. Pt/N-UNCD interfaces subjected to low loads during sliding demonstrated significant increases in contact resistance due to insulating film formation that was not observed at larger loads. Taken in concert, these finding demonstrate the capability of AFM to investigate nanoscale electrical contact phenomena without the need for time-consuming and expensive integration of unproven materials in NEMS logic switches

Ultra Thin AlN Piezoelectric Nano-Actuators

This paper reports the first implementation of ultra thin (100 nm) Aluminum Nitride (AlN) piezoelectric layers for the fabrication of vertically deflecting nano-actuators. An average piezoelectric coefficient (d31~ 1.9 pC/N) that is comparable to its microscale counterpart has been demonstrated in nanoscale thin AlN films. Vertical deflections as large as 40 nm have been obtained in 18 μm long and 350 nm thick cantilever beams under bimorph actuation with 2 V. Furthermore, in-plane stress and stress gradients have been simultaneously controlled. Leakage current lower than 2 nA/cm2 at 1 V has been recorded and an average relative dielectric constant of approximately 9.2 (as in thicker films) has been measured. These material characteristics and preliminary actuation results make the AlN nano-films ideal candidates for the realization of nanoelectromechanical switches for low power logic applications

Piezoelectric aluminum nitride nanoelectromechanical actuators

This letter reports the implementation of ultrathin (100 nm) aluminum nitride (AlN) piezoelectric layers for the fabrication of vertically deflecting nanoactuators. The films exhibit an average piezoelectric coefficient (d31~−1.9 pC/N), which is comparable to its microscale counterpart. This allows vertical deflections as large as 40 nm from 18 µm long and 350 nm thick multilayer cantilever bimorph beams with 2 V actuation. Furthermore, in-plane stress and stress gradients have been simultaneously controlled. The films exhibit leakage currents lower than 2 nA/cm2 at 1 V, and have an average relative dielectric constant of approximately 9.2 (as in thicker films). These material characteristics and actuation results make the AlN nanofilms ideal candidates for the realization of nanoelectromechanical switches for low power logic applications

Angle-Resolved Environmental X-Ray Photoelectron Spectroscopy: A New Laboratory Setup for Photoemission Studies at Pressures up to 0.4 Torr

The paper presents the development and demonstrates the capabilities of a new laboratory-based environmental X-ray photoelectron spectroscopy system incorporating an electrostatic lens and able to acquire spectra up to 0.4 Torr. The incorporation of a two-dimensional detector provides imaging capabilities and allows the acquisition of angle-resolved data in parallel mode over an angular range of 14° without tilting the sample. The sensitivity and energy resolution of the spectrometer have been investigated by analyzing a standard Ag foil both under high vacuum (10−8 Torr) conditions and at elevated pressures of N2 (0.4 Torr). The possibility of acquiring angle-resolved data at different pressures has been demonstrated by analyzing a silicon/silicon dioxide (Si/SiO2) sample. The collected angle-resolved spectra could be effectively used for the determination of the thickness of the native silicon oxide layer