Improvement of the Charge Retention of a Non-Volatile Memory by a Bandgap-Engineered Charge Trap Layer

In recent years, research based on HfO2 as a charge trap memory has become increasingly popular. This material, with its advantages of moderate dielectric constant, good interface thermal stability and high charge trap density, is currently gaining in prominence in the next generation of nonvolatile memory devices. In this study, memory devices based on a-IGZO thin-film transistor (TFT) with HfO2/Al2O3/HfO2 charge trap layer (CTL) were fabricated using atomic layer deposition. The effect of the Al2O3 layer thickness (1, 2, and 3 nm) in the CTL on memory performance was studied. The results show that the device with a 2-nm Al2O3 layer in the CTL has a 2.47 V memory window for 12 V programming voltage. The use of the HfO2/Al2O3/HfO2 structure as a CTL lowered the concentration of electrons near the tunnel layer and the loss of trapped electrons. At room temperature, the memory window is expected to decrease by 0.61 V after 10 years. The large storage window (2.47 V) and good charge retention (75.6% in 10 years) of the device under low-voltage conditions are highly advantageous. The charge retention of the HfO2/Al2O3/HfO2 trap layer affords a feasible method for fabricating memory devices based on a-IGZO TFT.

Electrocharging face masks with corona discharge treatment

We detail an experimental method to electrocharge N95 facepiece respirators and face masks (FMs) made from a variety of fabrics (including non-woven polymer and knitted cloth) using corona discharge treatment (CDT). We present practical designs to construct a CDT system from commonly available parts and detail calibrations performed on different fabrics to study their electrocharging characteristics. After confirming the post-CDT structural integrity of fabrics, measurements showed that all non-woven polymer electret and only some knitted cloth fabrics are capable of charge retention. Whereas polymeric fabrics follow the well-known isothermal charging route, ion adsorption causes electrocharging in knitted cloth fabrics. Filtration tests demonstrate improved steady filtration efficiency in non-woven polymer electret filters. On the other hand, knitted cloth fabric filters capable of charge retention start with improved filtration efficiency which decays in time over up to 7 h depending on the fabric type, with filtration efficiency tracking the electric discharge. A rapid recharge for a few seconds ensures FM reuse over multiple cycles without degradation.