High-performance broadband photoresponse of self-powered Mg2Si/Si photodetectors

Infrared optoelectronic devices are capable of operating in harsh environments with outstanding confidentiality and reliability. Nevertheless, suffering from the large band gap value, most semiconductor materials are difficult to detect infrared light signals. Here, Mg2Si/Si heterojunction photodetectors (PDs), which possess the advantages of low-cost, easy process, environmental friendliness, and compatibility with silicon CMOS technology, have been reported with a broadband spectral response as tested from 532 to 1550 nm under zero-bias. When the incident light wavelength is 808 nm, the Mg2Si/Si photodetector (PD) has a responsivity of 1.04 A/W and a specific detectivity of 1.51 × 1012 Jones. Furthermore, we find that the Ag nanoparticles (Ag_NPs) assembled on the Mg2Si layer can greatly improve the performance of the Mg2Si/Si PD. The responsivity and specific detectivity of Mg2Si/Si device with Ag_NPs under 808 nm illumination are 2.55 A/W and 2.60 × 1012 Jones, respectively. These excellent photodetection performances can be attributed to the high-quality of our grown Mg2Si material and the strong built-in electric field effect in the heterojunction, which can be further enhanced by the local surface plasmon effect and local electromagnetic field induced by Ag_NPs. Our study would provide significant guidance for the development of new self-powered infrared PDs based on silicon materials.

Design and Performance Verification of a Space Radiation Detection Sensor Based on Graphene

In order to verify the performance of a graphene-based space radiation detection sensor, the radiation detection principle based on two-dimensional graphene material was analyzed according to the band structure and electric field effect of graphene. The method of space radiation detection based on graphene was studied and then a new type of space radiation sensor samples with small volume, high resolution, and radiation-resistance was formed. Using protons and electrons, the electrical performance of GFET radiation sensor was verified. The designed graphene space radiation detection sensor is expected to be applied in the radiation environment monitoring of the space station and the moon, and can also achieve technological breakthroughs in pulsar navigation and other fields.

Quantum Study of Symmetrical/asymmetrical Chare/Energy Transfer in a Simple Candidate Molecular Switch

Based on molecular nanoelectronic knowledge, field-effect molecular electronic devices can be designed for use in nano-circuits. Therefore, in this study, a candidate field-effect molecular switch (isolated, M, and non-isolated, Au-M-Au/Au4-M-Au4, molecular systems) is studied, using density function/pseudopotential model (DFT/LANL2DZ). This molecular switch's switching mechanism (ON/OFF) we performed by applying an external electric field-effect. In this regard, some computational studies related to this molecular switch's electronic/vibrational transfer properties were investigated. Also, used from the quantum theory of atoms in the molecule (QTAIM), Landauer's theory (LT), and energy/charge transfer mechanisms were used at the atomic scale to predict this molecular switch's voltage-current (IV) behavior. Analysis of these results showed that when the intensity of the applied electric field increases to 0.008 au, the molecular switch is in the ON state. In addition, the role of gold electrodes on some of the electronic/vibrational properties of this molecular switch was investigated. Analysis of the results showed that gold electrodes play an essential role in the local distribution of charge and intramolecular energy and, consequently, the I/V diagram of this molecular switch. It is expected that such quantum-based research (without using numerical methods such as Green's function methods) could open new horizons in the quantum study of molecular parts at the atomic-intramolecular scale.

Residue Interactions Affecting The Deprotonation of Internal Guanine Moieties In Oligodeoxyribonucleotides, Calculated By FMO Methods

The effect of vicinal molecular groups on the intrinsic acidity of a central guanine residue in short single-stranded DNA models, and the potentials exerted by the backbone and the nucleobases on the leaving proton were determined by the Fragment Molecular Orbital (FMO) method, in terms of quantum descriptors (QD) and pair interaction interfragment decomposition analysis (PIEDA). The acidity of the central guanine moiety decreased with increasing oligonucleotide length, in response to changes by less than1 eV in the ionization potential, global softness, electrophilicity index and electronegativity descriptors. The differences in these descriptors were majorly interpreted in terms of the electrostatic influence of the negative charges residing on the backbone of the molecule. Additionally, this electric-field effect was determined explicitly for the displacement of the test hydronium ion to a distance of 250 Å from its original position, resulting in good agreement with calculations of the variation in Gibbs free energies, obtained from physical experiments conducted on the identical oligonucleotide sequences. The reported results are useful for biophysical applications of deoxyriboligonucleotides containing guanine residues in order to induce local negative charges at specific positions in the DNA chain.