Abstract-Integrating energy-harvesting photodiodes with logic and exploiting on-die interconnect capacitance for energy storage can enable new, ultraminiaturized wireless systems. Unlike CMOS imager pixels, the proposed photodiode designs utilize p-diffusion fingers and are implemented in a conventional logic process. Also unlike specialized solar cell processes, the designs utilize the on-chip metal interconnect to form a diffraction grating above the p-diffusion fingers which also provides capacitive energy storage. To explore the tradeoffs between optical efficiency and energy storage for integrated photodiodes, an array of photovoltaics with various diffractive storage capacitors was designed in a 90-nm CMOS logic process. The diffractive effects can be exploited to increase the photodiodes' response to off-axis illumination. Transient effects from interfacing the photodiodes with switched-capacitor DC-DC converters were examined, with measurements indicating a 50% reduction in the output voltage ripple due to the diffractive storage capacitance. A quantitative comparison between 90-nm and 0.35-µm CMOS logic processes for energy-harvesting capabilities was carried out. Measurements show an increase in power generation for the newer CMOS technology, however at the cost of reduced output voltage. One potential application for the integrated photodiodes is harvesting energy for a subdermal biomedical device.

A theoretical framework based on first-principles calculations is developed for the essential properties of the 3D ternary compound Li4Ti5O12, a Li+-based battery anode.

The rich magneto-electronic properties of AA-bottom-top (bt) bilayer silicene are investigated using a generalized tight-binding model. The electronic structure exhibits two pairs of oscillatory energy bands for which the lowest conduction and highest valence states of the low-lying pair are shifted away from the K point. The quantized Landau levels (LLs) are classified into various separated groups by the localization behaviors of their spatial distributions. The LLs in the vicinity of the Fermi energy do not present simple wave function modes. This behavior is quite different from other two-dimensional systems. The geometry symmetry, intralayer and interlayer atomic interactions, and the effect of a perpendicular magnetic field are responsible for the peculiar LL energy spectra in AA-bt bilayer silicene. This work provides a better understanding of the diverse magnetic quantization phenomena in 2D condensed-matter materials.

The three-dimensional ternary Li2GeO3 compound presents various unusual essential properties. The main features are thoroughly explored from the first-principles calculations. The concise pictures, the critical orbital hybridizations in Li–O and Ge–O bonds, are clearly examined through the optimal geometric structure, the atom-dominated electronic energy spectrum, the spatial charge densities, the atom and orbital-decomposed van Hove singularities, and the strong optical responses. The unusual optical transitions cover the red-shift optical gap, various frequency-dependent absorption structures and the most prominent plasmon mode in terms of the dielectric functions, energy loss functions, reflectance spectra, and absorption coefficients. Optical excitations, depending on the directions of electric polarization, are strongly affected by excitonic effects. The close combinations of electronic and optical properties can identify a significant orbital hybridization for each available excitation channel. The developed theoretical framework will be very useful in fully understanding the diverse phenomena of other emergent materials.

The essential properties of monolayer HfX2 (X = S, Se, or Te) are fully explored by first-principles calculations. The optimal lattice symmetries, sublattice buckling, electronic energy spectra, and density of states are systematically investigated. Monolayer HfS2, HfSe2, and HfTe2, respectively, belong to middle-gap semiconductor, narrow-gap one and semimetal, with various energy dispersions. Moreover, the van Hove singularities (vHs) mainly arise from the band-edge states, and their special structures in the density of states strongly depend on their two or three-dimensional structures and the critical points in the energy-wave-vector space. The above-mentioned theoretical predictions are attributed to the multi-orbital hybridizations of [dx2−y2, dxy, dyz, dzx, dz2]–[s, px, py, pz] in the Hf-X chemical bonds. The diversified physical phenomena clearly indicate a high potential for applications, as observed in MoS2-related emergent materials ions.