High-κ and metal gate structures have been used to improve the performance of CMOS devices. By changing the materials and structures of the gate dielectric stacks, the flatband voltage (VFB) and the leakage can be changed. We used bilayers and multilayer structures composed of MgO and Al2O3 to verify their influence on the overall electrical properties. Films with an MgO bottom layer generally are found with less flatband voltage shift and lower leakage than with an Al2O3 bottom layer. Also, the frequency dispersion and the interface state density (Dit) are higher for those with MgO bottom layers. MgO films thicker than 0.5 nm effectively shields the positive charges present in the Al2O3.

MOS capacitors with the ZrHfO/AlOx/ZrHfO high-k gate dielectric stack were prepared and characterized for memory functions. The device prefers to trap holes, i.e., under the negative gate voltage, rather than electrons, i.e., under the positive voltage. The hole-trapping process is time and voltage dependent. The weakly trapped holes are quickly released upon the remove of the stress voltage. However, more than 30% of the originally trapped holes can be retained in the device after 10 years. The AlOx embedded ZrHfO high-k stack is a suitable gate dielectric structure for nonvolatile memories.

Topological insulators are a new class of materials with the ability to carry spin-polarized currents on their surfaces. Nuclear magnetic resonance (NMR) measurements can probe the magnetic interactions between specific isotopes and the electronic system of a material. We present 209Bi NMR spectra and relaxation rate data on single crystals of the topological insulator material Bi2Se3 grown under various conditions. Our NMR data on single crystals reveal a significant strength of coupling between the nuclear spins and the bulk carrier spins, suggesting that nuclear spins may have a sizeable effect on spin-polarized surface currents.

A miniaturized frequency agile multi-band antenna based on BST varactors is presented. The radiation patterns and frequency responses of this antenna are characterized. The measured tunability was 2.1%, 9.1%, and 6.6% for the first, second, and third band respectively. The lowest resonant frequency corresponds to an antenna size of 0.076λg × 0.076λg. The size reduction of the antenna was achieved by employing the novel antenna structure and the thin film BST varactors. The measured -3 dB bandwidth was between 3.1% and 7.4% for all bands.

We report the first successful application of corona charging noncontact C-V and I-V metrology to interface and dielectric characterization of high-k/III-V structures. The metrology, which has been commonly used in Si IC manufacturing, uses incremental corona charge dosing, ΔQC, on the dielectric surface, and the measurement of surface voltage response, ΔVS, using a Kelvin-probe. Its application to In0.53Ga0.47As with a high-k stack required modifications related to the effects of dielectric trap induced voltage transients. The developed Corona Charge-Kelvin Probe Metrology adopted strictly differential measurements using ΔQC and ΔV, and corresponding differential capacitance rather than measurements based on total global charge, Q, and voltage, V, values.

Electrical characterization data including interface trap density, electrical oxide thickness, and dielectric leakage are presented for a sample containing an In0.53 Ga0.47 As channel overlaid with a bilayer (2nm Al2O3/5nm HfO2) dielectric stack that is considered to be very promising for application in performance NFETs with high-mobility channels.

Ho2O3-TiO2 based metal-insulator-metal capacitors were grown by ALD, using Ho(thd)3, Ti(OCH(CH3)2)4 and ozone as precursors. The thicknesses of the films were in the range of 7.7 to 25 nm. Some of the films were post-deposited annealed in order to study the treatment effects. The capacitors were electrically characterized. Leakage current decreases as the amount of holmium increased in the films. Resistive switching behavior was obtained in the samples where the leakage current was low. This effect was also observed in Ho2O3 films, where no titanium was present in the films.

The primary impediment to continued improvement of charge-based electronics is the excessive energy dissipation incurred in switching a bit of information. With suitable choice of materials, devices made of multiferroic composites, i.e., strain-coupled piezoelectric-magnetostrictive heterostructures, dissipate miniscule amount of energy of ∼1 attojoule at room-temperature, while switching in sub-nanosecond delay. Apart from devising memory bits, such devices can be also utilized for building logic, so that they can be deemed suitable for computing purposes as well. Here, we first review the current state of the art for building nanoelectronics using multiferroic composites. On a recent development, it is shown that these multiferroic straintronic devices can be also utilized for analog signal processing, with suitable choice of materials. By solving stochastic Landau-Lifshitz-Gilbert equation of magnetization dynamics at room-temperature, it is shown that we can achieve a voltage gain, i.e., these straintronic devices can act as voltage amplifiers.

We focused on the presence of water absorbed in the grain boundary of a polycrystalline transition metal oxide (TMO) film in an EL/poly-TMO/EL structure. The effect of supplying water to resistive random access memories (ReRAMs) of Pt/NiO/Pt structure on switching voltages and data retention characteristics was investigated. As a result, switching voltages were decreased by supplying water and reset switching was confirmed to be strongly induced by supplying water even at room temperature without applying voltage. These results suggest that water enhances resistive switching effect by providing reducing species and oxidizing species respectively such as H+ and OH-.

The connection between the bi-polar hafnia-based resistive-RAM (RRAM) operational characteristics and dielectric structural properties is considered. Specifically, the atomic-level description of RRAM, which operations involve the repeatable rupture/recreation of a localized conductive path, reveals that its performance is determined by the outcome of the initial forming process defining the structural characteristics of the conductive filament and distribution of the oxygen ions released from the filament region. The post-forming ions spatial distribution in the cell is found to be linked to a degree of dielectric oxygen deficiency, which may either assist or suppress the resistive switching processes.

Ferroelectric barium-strontium-titanate (BST) varactors are becoming extremely important particularly for frequency-agile RF and microwave circuits. Tunable bandstop filters are desired to eliminate unwanted signals for several communication systems. In this paper, a compact tunable bandstop filter (BSF) based on a single hairpin resonator, using ferroelectric BST varactors, is also presented. The frequency response of proposed BSF can be adjusted by increasing or decreasing the length, width, and space for the coupled line hairpin resonator. One pair of variable capacitors has been incorporated to the filter for tuning and miniaturization purposes. The notch frequency of BSF can be tuned from 705 MHz to 1.035 GHz with a tuning voltage of 6 Volts utilizing BST varactors.

Resistively switching devices have attracted great attention for potential use in future nonvolatile information storage. Among various oxide materials that show resistive switching (RS) behavior, SrTiO3 (STO) is regarded as a model material to study the effect of valence changes accompanying RS in the oxide [1]. In this class of materials, the RS effect is attributed to rely on the migration of oxygen vacancies and an associated valence change in the cation sublattice. To achieve a switchable state, an initial electroforming step is typically required, which is believed to create conductive regions in the insulating material [2]. Under high electrical stress, an oxygen-deficient region, often referred to as the virtual cathode (VC), is formed [3]. The RS occurs across a very short distance between the VC and the anode, allowing for very short switching times. As the electroforming step greatly impacts the device performance and switching variability, its understanding is essential for device optimization. Electroforming is affected by multiple parameters, e.g. voltage, current, temperature, dopant and defect concentrations, ambient gas atmosphere and time. Distinguishing the influence of the particular parameters is a desirable aim and challenging task. Electrocoloration of Fe-doped STO single crystals has proven a valuable means to visualize valence changes of the Fe ions and is thus suitable to study the formation of the VC. Therefore, we performed electrocoloration experiments and used high resolution transmission light optical microscopy to make the redoxprocesses during electroforming visible. The influence of process driving parameters on the evolution of the VC region is studied. The evolution of the VC is interpreted by drift-diffusion simulation of the time evolution of the oxygen vacancy distribution.