Modeling and fabrication of an RF MEMS variable capacitor with a fractal geometry

Elshurafa, Amro M.; Salama, Khaled N.; Ho, Pak Hung

doi:10.1109/iscas.2013.6572438

Cited by 8 publications

(4 citation statements)

References 12 publications

(17 reference statements)

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“…Non-linearity in applied force versus deflection was observed at larger deflections due to graphene stretching, with an example illustrated in Figure 3D). The force versus deflection relation F ∝ Eδ 3 can be modelled for different geometries with a virtual displacement method [25], curved plate varactor [26], vertical parallel plate [27], parallel plate with levers [28], simple parallel plate design [6], a comb finger varactor [7]. Further indicated in the graph are the ideal limits achievable in accordance with C/A = 0/h.…”

mentioning

confidence: 99%

“…A comparison between this work and different stateof the art MEMS varactors, with varactor gap h and area per unit capacitance A/C compared. The devices shown are state of the art silicon based MEMS varactors: with fractal structure[25], curved plate varactor[26], vertical parallel plate[27], parallel plate with levers[28], simple parallel plate design[6], a comb finger varactor[7]. Further indicated in the graph are the ideal limits achievable in accordance with C/A = 0/h.…”

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confidence: 99%

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Suspended graphene variable capacitor

Abdelghany¹,

Mahvash²,

Mukhopadhyay³

et al. 2016

2D Mater.

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The tuning of electrical circuit resonance with a variable capacitor, or varactor, finds wide application with the most important being wireless telecommunication. We demonstrate an electromechanical graphene varactor, a variable capacitor wherein the capacitance is tuned by voltage controlled deflection of a dense array of suspended graphene membranes. The low flexural rigidity of graphene monolayers is exploited to achieve low actuation voltage in an ultra-thin structure. Large arrays comprising thousands of suspensions were fabricated to give a tunable capacitance of over 10 pF/mm 2 , higher than that achieved by traditional micro-electromechanical system (MEMS) technologies. A capacitance tuning of 55% was achieved with a 10 V actuating voltage, exceeding that of conventional MEMS parallel plate capacitors. Capacitor behavior was investigated experimentally, and described by a simple theoretical model. Mechanical properties of the graphene membranes were measured independently using Atomic Force Microscopy (AFM). Increased graphene conductivity will enable the application of the compact graphene varactor to radio frequency systems.Mechanically tuned variable capacitance has been an effective means to tune resonant circuits since the advent of radio [1]. More compact varactors have since been developed in the form of an electrically tuned semiconductor junction capacitance [2]. Micro-electromechanical system (MEMS) implementations of varactors [3] combine the advantages of mechanical and semiconductor varactors in a single device architecture, including high electrical quality factor, high linearity, and the capacity for monolithic integration with silicon electronics [4]. The canonical MEMS varactor is the parallel plate structure consisting of a conducting membrane suspended over a fixed plate, actuated by electrostatic attraction under an applied bias potential. While simple in structure, typical parallel plate varactors suffer high operating voltage [5,6] and a limited capacitive tuning range. These limitations are typically overcome by complex mechanisms [7], which increase both the size and actuation voltage.Fundamentally, increasing the flexibility of a suspended element by reducing it's thickness will reduce the actuation voltage of a parallel plate varator [8]. Monolayer graphene membranes achieve the ultimate limit with an inferred elastic stiffness of E e 390 N/m [9]. In comparison a 15 nm thick Si 3 N 4 membrane has an elastic stiffness of E e 6.3 kN/m. In addition to lower actuation voltage, graphene nano-electromecanical systems (NEMS) occupy less area than traditional MEMS counterparts [10], and can be easily integrated with integrated silicon electronics using standard transfer techniques [11,12]. In the last decade, graphene NEMS have been widely investigated, including suspended graphene resonators [13][14][15], switches [16][17][18], and sensors [9]. While the theoretical limits of suspended graphene varactors has been investigated [8], large arrays of low spring constant suspensions has be...

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Suspended graphene variable capacitor

Abdelghany¹,

Mahvash²,

Mukhopadhyay³

et al. 2016

2D Mater.

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“…Upon reaching this particular stage of the simulation operation, error notifications are presented to the user, subsequently leading to the termination of the procedure. As a result, the simulation must revolve around the Vpi, yielding an adequate approximation to the Vpi (Elshurafa et al, 2013). The figures denoted as 3 (d, e) present the 3-dimensional device layout of the simulated NEM switch.…”

Section: Results Analysismentioning

confidence: 99%

Sub-0.3 volt amorphous metal WNx based NEMS switch with 8 trillion cycles

Mayet,

Muqeet,

Alhashim

et al. 2024

Front. Mater.

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Introduction: The mechanical nature of nanoelectromechanical (NEM) switches makes them sluggish yet desirable for ultra-low-power, harsh environment applications. Two- and three-terminal NEM switches have been demonstrated using onedimensional, two-dimensional, and thin films, but sub-0.3 V operation with improved mechanical and electrical reliability is still elusive.Method: This study presents WNxnano-ribbon-based NEM sensor switches that operate at 0.6 V, 30 nanosecond switching time, 8 trillion cycles, and 0.5 mA ON current with less than 5 kΩ ON resistance, without stiction, mechanical welding, or short circuits. WNx’s high Young’s modulus gives it great elasticity and mechanical restoring force, which may overcome van der Waal and capillary forces.Results and Discussion: With its high Young’s modulus, the device’s nanoscale size facilitated low operating voltage. WNxnano-ribbon without grain boundaries is amorphous and more mechanically strong. Hammering and high current flow may destroy the nano-ribbon contact surface and interface, which is practically immaculate. Pull-out time (dominant delay factor) is 0 owing to high Young’s modulus, hence hysteresis loss and delay are absent. Elasticity and Young’s modulus increase speed.

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“…As a result, these capacitive sensors have been implemented in many applications, including biomedical detection and have shown good results [7][8][9][10]. One type of capacitive sensor is the fractalshaped capacitor, which is reported to have less residual stress and provide a uniform distribution of the electrical field [11][12][13]. This can play a major role in EWOD systems.…”

Section: Introductionmentioning

confidence: 99%