Physically transient electronic devices that can disappear on demand have great application prospects in the field of information security, implantable biomedical systems, and environment friendly electronics. On the other hand, the memristor-based artificial synapse is a promising candidate for new generation neuromorphic computing systems in artificial intelligence applications. Therefore, a physically transient synapse based on memristors is highly desirable for security neuromorphic computing and bio-integrated systems. Here, this is the first presentation of fully degradable biomimetic synaptic devices based on a W/MgO/ZnO/Mo memristor on a silk protein substrate, which show remarkable information storage and synaptic characteristics including long-term potentiation (LTP), long-term depression (LTD) and spike timing dependent plasticity (STDP) behaviors. Moreover, to emulate the apoptotic process of biological neurons, the transient synapse devices can be dissolved completely in phosphate-buffered saline solution (PBS) or deionized (DI) water in 7 min. This work opens the route to security neuromorphic computing for smart security and defense electronic systems, as well as for neuro-medicine and implantable electronic systems.

A bio-inspired physically transient/biodegradable synapse for security neuromorphic computing based on memristors.

Defect characterization for epitaxial HgCdTe alloys by electron microscopy

We found that the write-once-read-many-times (WORM, inerasable)-to-rewritable (erasable) transition phenomenon results from the different structures of the filament, which is determined by the grain orientations of the deposited films. The conduction mechanism of this switching transition and its impact on the synaptic behavior in various ZnO nanostructures are also discussed. Furthermore, our WORM devices have a programmable physical damage function that can be exploited for use in security systems against data theft, hacking, and unauthorized use of software/hardware. This work proposes ZnO-based nonvolatile memory for invisible electronic applications and gives valuable insight into the design of WORM and rewritable memories.

Film-Nanostructure-Controlled Inerasable-to-Erasable Switching Transition in ZnO-Based Transparent Memristor Devices: Sputtering-Pressure Dependency

First-principles investigations of Mn doped zinc-blende ZnO based magnetic semiconductors: materials for spintronic applications

We performed a comprehensive investigation on the influence of oxygen vacancies (VO) defects and their evolution under Mn substitution and thermal annealing in different atmospheres on the ferromag...

Influence of Oxygen Defects and Their Evolution on the Ferromagnetic Ordering and Band Gap of Mn-Doped ZnO Films

The nucleation and growth of Hg1−xCdxTe on CdTe(211)B/Si(211) substrates by molecular beam epitaxy are comprehensively studied by in situ reflection high energy electron diffraction and transmission electron microscopy. Microtwins are observed to be formed at the interface, but are overgrown later as the growth proceeds. It is shown that the three-dimensional growth at the nucleation stage of HgCdTe on CdTe(211)B/Si and CdZnTe(211)B is more likely due to the higher surface energy of Hg1−xCdxTe than that of CdTe(211)B and CdZnTe(211)B.

Molecular beam epitaxial growth and structural properties of HgCdTe layers on CdTe(211)B/Si(211) substrates

Write-once-read-many-times memory (WORM) devices were fabricated using ZnO and ZnO/MgO as active layers on Si. Devices fabricated with ZnO show a different memory effect at different current compliances such as WORM at 100 $\mu \text{A}$ , 500 $\mu \text{A}$ , and 1 mA, resistive switching (RS) instead of WORM at 5 and 10 mA, and WORM and RS coexisting at 20, 50, and 100 mA, while devices fabricated with ZnO/MgO show WORM only at all current compliances. A few nanometers of MgO layer play a major role in preventing devices from reset at all current compliances because the much lower drift velocity of oxygen vacancy in MgO and accumulation of negatively charged O2− ions at the interface between ZnO and MgO prevent the conducting filaments composed of oxygen vacancies from breaking.

Metal/ZnO/MgO/Si/Metal Write-Once-Read-Many-Times Memory

Strong room-temperature ferromagnetism is demonstrated in single crystalline Mn-doped ZnO grown by molecular beam epitaxy. With a low Mn concentration of 2 × 1019 cm−3, Mn-doped ZnO films exhibited room-temperature ferromagnetism with a coercivity field larger than 200 Oe, a large saturation moment of 6 μB/ion, and a large residue moment that is ∼70% of the saturation magnetization. Isolated ions with long range carrier mediated spin-spin coupling may be responsible for the intrinsic ferromagnetism.

Strong room-temperature ferromagnetism of high-quality lightly Mn-doped ZnO grown by molecular beam epitaxy

Strong room-temperature ferromagnetism is demonstrated in single crystalline Mn-doped ZnO thin films grown by molecular beam epitaxy. Very low Mn doping concentration is investigated, and the measured magnetic moment is much larger than what is expected for an isolated ion based on Hund's rules. The ferromagnetic behavior evolves with Mn concentration. Both magnetic anisotropy and anomalous Hall effect confirm the intrinsic nature of ferromagnetism. While the Mn dopant plays a crucial role, another entity in the system is needed to explain the observed large magnetic moments.

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Yan Xin

Papers

Molecular beam epitaxial growth and structural properties of HgCdTe layers on CdTe(211)B/Si(211) substrates

Metal/ZnO/MgO/Si/Metal Write-Once-Read-Many-Times Memory

Strong room-temperature ferromagnetism of high-quality lightly Mn-doped ZnO grown by molecular beam epitaxy

Peculiarly strong room-temperature ferromagnetism from low Mn-doping in ZnO grown by molecular beam epitaxy