Understanding the influences of defect states on gas adsorption on graphene is at the heart of developing graphene based gas sensors for practical applications. However, it has been challenging to experimentally discriminate the gas adsorptions induced by the defects on graphene, especially the charged impurities commonly found on the transferred graphene samples. Here, using a graphene transistor biased with the quasistatic gate voltage, this study experimentally measures the charge density and the scattering strength of the gas adsorbents on graphene and directly resolves the defect‐induced versus intrinsic gas adsorption processes on graphene for the first time. Furthermore, the elimination and the tuning of the defect‐induced gas adsorptions on graphene are also demonstrated via the chemical compensation process and the gate voltage technique, respectively. These findings provide critical experimental proofs and a versatile platform for understanding and manipulating the defect‐gas interactions on graphene, and could advance the developments of defect‐free and label‐free gas sensing applications using graphene transistors.

High-temperature processes, such as packaging and annealing, are challenges for Radio-Frequency Micro-Electro-Mechanical-Systems (RF MEMS) structures, which could lead to device failure. Coefficient of thermal expansion (CTE) mismatch and the material’s creep effect affect the fabrication and performance of the MEMS, especially experiencing the high temperature. In this paper, the Thermal–Mechanical-Stress-Creep (TMSC) effect during thermal processes from room temperature (RT) to 200 °C is modeled and measured, in which an Au-cantilever-based RF MEMS switch is selected as a typical device example. A novel Isolation-Test Method (ITM) is used to measure precise TMSC variation. This method can achieve resolutions of sub-nanometer (0.5 nm) and attofarad (1 aF). There are three stages in the thermal processes, including temperature ramping up, temperature dwelling, and temperature ramping down. In different stages, the thermal–mechanical stress in anchor and cantilever, the grain growth of gold, and the thermal creep compete with each other, which result in the falling down and curling up of the cantilever. These influencing factors are decoupled and discussed in different stages. The focused ion beam (FIB) is used to characterize the change of the gold grain. This study shows the possibility of predicting the deformation of MEMS structures during different high-temperature processes. This model can be extended for material selection and package temperature design of MEMS cantilever in the further studies.

The increasing demand for satellite communication necessitates efficient resource management, especially as next-generation high-throughput satellites (HTSs) face challenges in optimizing user connections. This paper presents a novel method that integrates a discretely improved Particle Swarm Optimization (PSO) algorithm with a dynamic task management framework to enhance satellite resource allocation efficiency. The PSO algorithm is adapted for discrete selection problems to maximize a fitness function based on user priority, user preference, and capacity satisfaction, thus ensuring accurate user–satellite matching. A main loop function iteratively updates user data and connection statuses, thus achieving continuous optimization of satellite connections. Through simulation studies, we validated the effectiveness of this method under dynamically changing user demands, demonstrating that the Discrete PSO algorithm significantly outperforms Simulated Annealing (SA) and the Genetic Algorithm (GA) in user satisfaction, maintaining levels above 0.996 even under high demand. Additionally, it effectively prioritizes high-demand users, ensuring their satisfaction remains above 0.95. Overall, our method enhances the management of daily communication tasks, significantly improving service quality and user satisfaction.

Cantilevers are widely used as actuators and sensors in microelectromechanical system (MEMS) devices. The creep behavior of cantilevers is an important factor in the lifetime of a MEMS device. This study examines the creep phenomenon in metal-based MEMS cantilever devices and deformations of the cantilever were investigated at different temperatures. A Generalized-Accumulated-Temperature (GAT) parameter is introduced into the MEMS field for characteristic prediction, particularly for high-temperature storage lifetime prediction. Simplified radio frequency (RF) MEMS devices were designed, fabricated, and measured to investigate thermal creep. The devices were fabricated by surface micromachining processes at room temperature, strictly without any extra thermal effect before testing. The devices were tested with nanometer accuracy using the in-situ co-test method with three-dimensional (3D) optical microscope and RF probe station. The test results of the device with a gold-alloy cantilever showed that the deformation rate increased with temperature raising, and the logarithm of the rate exhibited a linear relationship with the temperature. A mathematical relation between the GAT parameter and cantilever deformation was established by which the lifetime of the cantilever can be predicted at different temperatures. The performances of pure gold and gold alloy were compared, and the alloy shows better thermal stability. This study shows that the gold alloy is more suitable on lifetime than pure gold for use as cantilevers. The GAT parameter introduced in this paper can enable the realization of metal-cantilever-based MEMS devices. It can also be widely used in other MEMS devices as a generic time–temperature parameter. 2023-0054

With the booming development of satellite applications, the giant constellations of low Earth orbit (LEO) satellites have introduced challenges for the data relay service. The multi-beam satellite not only offers concurrent access to a large number of objects, but can also meet the high data requirements toward specific coverage of the LEO constellation. However, the multi-beam satellite often faces the mismatch problem of spot allocation and data requirements, which can cause an overload traffic jam or a waste of resources. An optimization algorithm on spot beam allocation is necessary to automatically place the spot centers with appropriate beam widths in line with the density of the traffic demands and to realize the uniformity of the beam occupation. Compared with the conventional K-means algorithm, two adjustable parameters α and β are introduced: one for tuning the ratio of two components making up the distance matrix, and the other for setting the obligatory minimum number of objects per beam. In this paper, the whole process of the proposed method is demonstrated, including the establishment of the low-orbit satellite constellation model, the extraction of the distribution features, and the implementation and evaluation of the modified K-means algorithm. The results prove the validity of the proposed algorithm. A larger value of β with a relative smaller value of α tends to obtain the uniformity of beam occupation; the minimum standard deviation of objects per beam is achieved when α is 0.2 and β is 0.8. This demonstrates that the uniformity of objects per beam can be realized by adjusting the parameters of the distance determination matrix and the obligatory minimal number of objects in each beam. The impact of parameter range on the results is also analyzed.

This paper proposes a series of optimized scalable contact-capacitive radio frequency micro- electro-mechanical systems (RF MEMS) switches for millimeter wave applications. Due to the contact-capacitive topology, the ON-state and OFF-state of the switch can be designed separately to obtain smaller $C_{ON}$ and larger $C_{OFF}$ , which results in high capacitance ratio ( $C_{r}$ ). The $C_{ON}$ is defined by capacitance of the contacts, and it is optimized for low insertion loss ( $IL_{ON}$ ). The $C_{OFF}$ is defined by the metal-insulator-metal (MIM) capacitor, and it is designed for working band and scalable performance. The measurements of the fabricated devices show acceptable agreements with design and simulation. The optimized switches perform well with $IL_{ON}$ better than 1.5dB and capacitive ratio about 124. The switches follow scaling rules from 20GHz to 110GHz. Linearity (IIP3) of the switches are tested to be higher than 60dBm, and calculated to be higher than 80dBm. Performances of the switch can be further improved and optimized in the future study.