The rapid evolution of electronic devices has highlighted the importance of innovative energy harvesting technologies and self-powered sensors to address the global energy crisis. Among these, triboelectric nanogenerators have emerged as a transformative solution for converting mechanical energy into electrical energy. This work presents the development of a novel multi-phase triboelectric nanogenerator (MP-TENG) designed to harvest mechanical energy from rotating machine components to power sensors, charge batteries, and enable condition monitoring and rotational speed sensing. A comprehensive mathematical model is established to elucidate the underlying physics governing the MP-TENG's operation. The device is fabricated using polytetrafluoroethylene (PTFE) and fur as tribo-pairs. Performance evaluation at various rotational speeds (100, 200, 300, and 400 rpm) reveals a direct correlation between rotational speed and the open-circuit voltage of the MP-TENG. Functionality of the developed MP-TENG is showcased by integrating it with drilling machine to power a watch. Moreover, MP-TENG is demonstrated as a self-powered wind speed sensor by correlating the open circuit of TENG with the wind speed of the fan. Experimental results confirm the MP-TENG's capability to deliver substantial electrical output, particularly at low frequencies, positioning it as a promising technology for energy harvesting from rotating machinery and self-powered speed sensing applications.
Environmentally friendly solar cells using AgGaTe2 as the light-absorbing layer has been prepared using the close-space sublimation (CSS) method. In Cu(In, Ga)Se2 solar cells, which has a similar structure to AgGaTe2, results exceeding 20% efficiency have been reported by using Ga-rich CIGS thin films. Therefore, in this study, AgGaTe2 thin films were adjusted to Ga-rich layers without deteriorating the quality of the solar cell structure. In previous work, extending the sublimation CSS time from 3 to 45 min enabled the fabrication of Ga-rich AgGaTe2 thin films and improved conversion efficiency. However, this also increased the number and size of holes in the films, deteriorating the interface quality. To resolve this issue and fabricate Ga-rich AgGaTe2 thin films with improved quality, two approaches were considered. First, the CSS sublimation time was decreased to 15 min to suppress excessive heating. Second, the amount of source material was increased to ensure sufficient Ga sublimation even with a shorter sublimation time. Increasing the source material alone did not result in a Ga-rich film; instead, the film remained nearly stoichiometric. However, reducing the sublimation time from 45 to 15 min improved the film quality, increasing the conversion efficiency from 1.21% to 2.48%.
In this work, we present the theory and modeling framework of a diamond optically gated junction field-effect transistor (DOGFET). The device utilizes nitrogen substitutional centers in type-1b diamond to optically modulate a p- boron doped diamond channel. Using sub-gap lasers with intensities as low as 100 W/cm , electrons are optically excited from substitutional nitrogen sites to the conduction band of the diamond substrate, thus enabling the optical gate to exercise control on modulating the space-charge region at the junction and therefore the channel conductivity. We show that the device can deliver a current of 7 m, or equivalently 1750 A/cm, while switching at a frequency greater than 100 kHz, in a form factor of 5 . The breakdown voltage is found to be greater than 1850 V, with a breakdown field strength of 13 MV/cm. Moreover, the device supports nonvolatile operation with a "memory effect" enabling single transistor state retention. The presented simulation framework provides a physically grounded insight into the limits and opportunities of optoelectronic diamond systems.
Next generation of quantum computers calls for reduced dc power dissipation of the cryogenic low-noise amplifier (LNA) applied in reading out the superconducting qubits. This article reports on processing and evaluation of a 100-nm gate length indium phosphide high electron mobility transistor (InP HEMT) technology used in the design of such LNAs. InP HEMTs with size of 4 & times; 50 & micro;m were measured on-wafer by DC and S-parameter characterization. Device noise performance was indirectly evaluated by measuring and modeling the gain and noise of a three-stage hybrid 4-8 GHz cryogenic LNA equipped with the InP HEMTs. When operating the LNA at a DC power of 2.1 mW, the InP HEMT LNA average noise temperature was 1.4 K with an average gain of 41.6 dB. The minimum noise temperature of the InP HEMT was estimated to be 1.1 K at 6 GHz. The performance achieved for the InP HEMT LNA is comparable to the LNAs currently used in quantum computing while requiring only 27% of the DC power consumption. Small-signal modeling of the InP HEMT suggested that this was due to a low output conductance associated with a large gate-recess length used in device fabrication.
SiSn and GeSn semiconductors are attracting much attention for their application in electronic and optoelectronic devices. However, the fundamental understanding of material properties of Sn-doped Si (Ge) alloys is still insufficient. To address this, we use density functional theory calculations to examine (1) the formation energy (E-f) and the thermal equilibrium concentration (C-eq) of Sn atoms in the bulk and near the (001) surface of Si (Ge) and (2) the stable configuration of Sn atoms in the bulk of Si (Ge). The important results in study (1) are that the C-eq of substitutional Sn (Sn-s) atoms is determined as 8.08 x 10(22)exp(-0.671 eV/kT) cm(-3) and 8.68 x 10(22)exp(-0.272 eV/kT) cm(-3) for bulk Si and Ge, respectively. The reliable E-f of interstitial Sn (Sni) atoms indicated that the Sn-i is not incorporated into Si and Ge matrices during film growth. The important result in study (2) is that preferential sites of Sn-s atoms in Si and Ge are determined up to 50% Sn composition. A new structure of Ge0.5Sn0.5 is discovered that is more stable than a zinc blende structure. More metastable structures containing Sn-Sn bonds exist in Si than in Ge at 37.5% and 50% Sn compositions.
