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The device concept of ferroelectric-based negative capacitance (NC) transistors offers a promising route for achieving energy-efficient logic applications that can outperform the conventional semiconductor technology, while viable operation mechanisms remain a central topic of debate. In this work, we report steep slope switching in MoS2 transistors back-gated by single-layer polycrystalline PbZr0.35Ti0.65O3. The devices exhibit current switching ratios up to 8 × 106 within an ultra-low gate voltage window of V g = ± 0.5 V and subthreshold swing (SS) as low as 9.7 mV decade−1 at room temperature, transcending the 60 mV decade−1 Boltzmann limit without involving additional dielectric layers. Theoretical modeling reveals the dominant role of the metastable polar states within domain walls in enabling the NC mode, which is corroborated by the relation between SS and domain wall density. Our findings shed light on a hysteresis-free mechanism for NC operation, providing a simple yet effective material strategy for developing low-power 2D nanoelectronics. [ABSTRACT FROM AUTHOR]

The various effects of the dc resistance, metallization thickness and geometry on the performance of the X-band tunable filters with ferroelectric varactors are analyzed. The filters are shown to exhibit high performance on the presence of thin metal near the varactors.

This paper reports on a comparison of gold and Gold--nickel alloys as contact materials for microelectromechanical systems (MEMS) switches. Pure gold is commonly used as the contact material in low-force metal-contact MEMS switches. The top two failure mechanisms of these switches are wear and stiction, which may be related to the material softness and the relatively high surface adhesion, respectively. Alloying gold with another metal introduces new processing options to strengthen the material against wear and reduce surface adhesion. In this paper, the properties of Au--Ni alloys were investigated as the lower contact electrode was controlled by adjusting the nickel content and thermal processing conditions. A unique and efficient switching degradation test was conducted on the alloy samples, using pure gold upper microcontacts. Solid-solution Au-Ni samples showed reduced wear rate but increased contact resistance, while two-phase Au--Ni (20 at.% Ni) showed a substantial improvement of switching reliability with only a small increase of contact resistance. Discussion of the effects of phase separation, surface topography, hardness, and electrical resistivity on contact resistance and switch degradation is also included. [2008-0049] Index Terms--Alloys, Au-Ni alloys, electrical contacts, microelectromechanical systems (MEMS), microswitch, radio-frequency (RF) MEMS.

A series of experiments was performed to characterize RF microelectromechanical system switch performance under variable environmental conditions and cryogenic temperatures. Data were recorded in helium and nitrogen environments to lower stiction failure rates as well as to circumvent switch bouncing arising from low pressure at cryogenic temperatures. Contact resistance values were observed to be lower at cryogenic temperatures but still two orders of magnitude higher than the values predicted for the constriction resistance of gold asperity contacts, consistent with the presence of adsorbed films on the contacts. An asperity-heating model was applied, from which it was deduced that contact voltages can selectively disassociate adsorbed films from the contact surface while not softening the gold asperity contacts. The results are consistent with the reduced mobility of the adsorbed surface films at cryogenic temperatures. [2007-0217] Index Terms--Contact resistance, electrical contacts, microelectromechanical systems (MEMS), RF MEMS, switches.

A tunable third-order combline bandpass filter using thin-film barium-strontium-titanate varactors and fabricated on a sapphire substrate is reported. Application of 0-200-V bias varied the center frequency of the filter from 2.44 to 2.88 GHz (16% tuning) while achieving a 1-dB bandwidth of 400 MHz. The insertion loss varied from 5.1 dB at zero bias to 3.3 dB at full bias, while the return loss exceeded 13 dB over the range. The third-order intercept of the filter was found to be 41 dBm. Index Terms--Barium strontium titanate (BST), combline filter, ferroelectric films, intermodulation distortion, microstrip filters, resonators, thin-film devices, tunable filters, varactor.

Interface SiO2 can be consumed by a reaction with a lanthanum oxide to form a silicate and it is shown that a temperature as low as 400 degree centigrade is enough t consume an interfacial SiO2 layer and this reaction is a viable pathway to achieve equivalent oxide thickness (EOTs) below 1.0 nm for MIS devices. The elimination of the silica interface is show by high-angle annular dark-field (HAADF) imaging in scanning transmission electron microscopy (STEM) in combination with electron energy-loss spectroscopy (EELS) and by medium-energy ion-scattering (MEIS) spectroscopy.

Tunable lowpass and bandpass lumped-element filters employing barium--strontium-titanate (BST)-based capacitors are presented. A new metallization technique is used, which improves the quality factor of the tunable BST capacitors by a factor of two. The lowpass filter has an insertion loss of 2 dB and a tunability of 40% (120-170 MHz) with the application of 0-9-V dc bias. The bandpass filter (BPF) has an insertion loss of 3 dB and a tunability of 57% (176-276 MHz) with the application of 0-6 V dc. The third-order intercept point of the BPF was measured to be 19 dBm with the application of two tones around 170 MHz. Index Terms--Barium-strontium-titanate (BST), ferroelectric, intermodulation distortion, metalorganic chemical vapor deposition (MOCVD), multilayer ground plane, paraelectric, tunable bandpass filter (BPF), tunable lowpass filter (LPF).