An intensive study has been performed to understand and tune deep reactive ion etch (DRIE) processes for optimum results with respect to the silicon etch rate, etch profile and mask etch selectivity (in order of priority) using state-of-the-art dual power source DRIE equipment. The research compares pulsed-mode DRIE processes (e.g. Bosch technique) and mixed-mode DRIE processes (e.g. cryostat technique). In both techniques, an inhibitor is added to fluorine-based plasma to achieve directional etching, which is formed out of an oxide-forming (O 2) or a fluorocarbon (FC) gas (C 4 F 8 or CHF 3). The inhibitor can be introduced together with the etch gas, which is named a mixed-mode DRIE process, or the inhibitor can be added in a time-multiplexed manner, which will be termed a pulsed-mode DRIE process. Next, the most convenient mode of operation found in this study is highlighted including some remarks to ensure proper etching (i.e. step synchronization in pulsed-mode operation and heat control of the wafer). First of all, for the fabrication of directional profiles, pulsed-mode DRIE is far easier to handle, is more robust with respect to the pattern layout and has the potential of achieving much higher mask etch selectivity, whereas in a mixed-mode the etch rate is higher and sidewall scalloping is prohibited. It is found that both pulsed-mode CHF 3 and C 4 F 8 are perfectly suited to perform high speed directional etching, although they have the drawback of leaving the FC residue at the sidewalls of etched structures. They show an identical result when the flow of CHF 3 is roughly 30 times the flow of C 4 F 8 , and the amount of gas needed for a comparable result decreases rapidly while lowering the temperature from room down to cryogenic (and increasing the etch rate). Moreover, lowering the temperature lowers the mask erosion rate substantially (and so the mask selectivity improves). The pulsed-mode O 2 is FC-free but shows only tolerable anisotropic results at −120 • C. The downside of needing liquid nitrogen to perform cryogenic etching can be improved by using a new approach in which both the pulsed and mixed modes are combined into the so-called puffed mode. Alternatively, the use of tetra-ethyl-ortho-silicate (TEOS) as a silicon oxide precursor is

Li and Na metals have the highest theoretical anode capacity for Li/Na batteries, but the operational safety hazards stemming from uncontrolled growth of Li/Na dendrites and unstable electrode-electrolyte interfaces hinder their real-world applications. Recently, the emergence of 3D conductive scaffolds aimed at mitigating the dendritic growth to improve the cycling stability has gained traction. However, while achieving 3D scaffolds that are conducive to completely prevent dendritic Li/Na is challenging, the routes proposed to fabricate 3D scaffolds to date are often complex and expensive. This not only leads to suboptimal battery performance but can make the manufacturing nearly unachievable, compromising their commercial viability. We herein introduce a facile and single-step route to honeycomb-like 3D porous Ni@Cu scaffolds via a hydrogen bubble dynamic template (HBDT) electrodeposition method. The current collectors fabricated by this method offer highly stable cycling performance of Li plating/stripping (> 300 cycles at 0.5 mAh cm-2 and over 200 cycles at 1.0 mAh cm-2), attributed to their ability to effectively accommodate Li/Na deposits in their porous networks and to delocalize the charge distribution. The beneficial role of LiNO3 as an electrolyte additive in improving the mechanical integrity of solid electrolyte interface (SEI) and mechanistic insights into how the 3D porous structure facilitates Li/Na plating/stripping are comprehensively presented. Finally, with an outstanding cycling performance of reversible Na deposition (over 240, 110 and 50 cycles for 0.5, 1.0 and 2.0 mAh cm-2 at 1.0 mA cm-2), our findings open new doors to expedite the development of Li/Na metal battery technology.

In common hybrid solid electrolytes (HSEs), either the ionic conductivity of the polymer electrolyte is enhanced by the presence of a nanosized inorganic filler, which effectively decrease the glass-transition temperature, or the polymer solid electrolyte acts mostly as a flexible host for the inorganic solid electrolyte, the latter providing the conductivity. Here a true HSE is developed that makes optimal use of the high conductivity of the inorganic solid electrolyte and the flexibility of the polymer matrix. It is demonstrated that the LAGP (Li1.5Al0.5Ge1.5(PO4)3) participates in the overall conductivity and that the interface environment between the poly­(ethylene oxide) (PEO) and LAGP plays a key role in utilizing the high conductivity of the LAGP. This HSE demonstrates promising cycling versus Li-metal anodes and in a full Li-metal solid-state battery. This strategy offers a promising route for the development of Li-metal solid-state batteries, aiming for safe and reversible high-energy-density batteries.

A detailed study is performed to understand and show the potential of high-speed, deep reactive ion etching (DRIE) of silicon using oxygen inhibitor pulses as a replacement for hydro-fluorocarbons (HFCs). This process might be considered the 'holy grail' in DRIE as the environmental restrictions for the use of HFCs are becoming increasingly stronger. When compared to the usual cryogenic mixed oxygen DRIE and with respect to profile control, the proposed cryogenic pulsed oxygen DRIE is virtually independent of silicon loading, mask material and trench width, and it is less prone to the formation of black silicon (BS). Some indication is found that one of the major causes for the formation of BS is the existence of dust inside the plasma. Dust is created when oxygen and silicon tetra fluoride (SiF 4 being the reaction product of silicon etching) coincide inside the plasma glow. This occurs in mixed oxygen plasma; the silica dust falls onto the wafer where it starts to form BS when directional etching is requested. Dust particles can also form when strong polymerizing gases are fed into the plasma. This is the case for the Bosch process using HFC pulses forming carbonic dust. The particles, and consequently the BS, are observed to be limited when the SiF 4 and O 2 gases are time separated, which forms the basis of the proposed pulsed oxygen DRIE. Another advantage of pulsed oxygen DRIE with respect to Bosch processing is that the protective skin of the sidewall during etching-a kind of native oxide-is believed to be self-terminating. This makes the process insensitive to profile variations caused by parameter fluctuations. It is found that inhibiting oxygen pulses give excellent results with respect to profile control at cryogenic temperatures (between −120 and −80 • C) and can still compete with HFC pulses up to intermediate low temperatures (between −80 and −40 • C). When selecting the proper DRIE conditions, the oxygen pulsed mode performs with excellent profile verticality and selectivity while keeping the silicon clean. It also shows a high etch rate up to 25 μm min −1 (<1% Si load of a 100 mm wafer). When the temperature is raised further (between −40 and 0 • C), the strength of the oxygen sidewall protection progressively fails and more oxygen with more bias is needed to keep sufficient profile directionality. The use of stronger oxide-forming agents is suggested in order to enable good performance at the more convenient, higher temperature, low bias conditions.

Titania (TiO2) offers a high theoretical capacity of 336 mAh g–1 with the insertion of one Li per Ti unit. Unfortunately, the poor ionic and electronic conductivity of bulk TiO2 electrodes limits its practical implementation. Nanosizing titania below ∼20 nm has shown to increase the rate performance and accessible capacity but still not more than 75% of the theoretical capacity at 1 C. In this work, we discovered that chlorine doping of amorphous TiO2 (TiO2–x Cl2x ) can achieve a high capacity without the need for nanosizing. By in situ doping during atomic layer deposition, an unprecedented 90% of the theoretical capacity was achieved at 1 C for 100 nm thick films. Even at a charging rate of 20 C, 40% of the maximum capacity was accessible for the film with highest Cl-content (x = 0.088). The capacity was found linearly dependent on the chloride content for a Cl/Ti atomic ratio from 0.06 to 0.09. The enhanced insertion kinetics are ascribed to enhanced electronic conductivity and facilitated Li+-ion diffusion as a result of Cl-doping. Furthermore, the potential of TiO2–x Cl2x films as high rate anode were demonstrated on micropillar electrodes in a half-cell configuration using a liquid electrolyte solution, showing 10 times higher capacity at 10 C compared to the literature.