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In this paper we present an investigation of the influence of nanoindentation location on the top surface of silicon micro-pillar. This silicon micro-pillar array which will be employed as a micro force sensor array based on three-dimension silicon (3D Si) structures, is fabricated by near UV nanoimprint lithography (NIL) technique and etched by Cryogenic Inductively Coupled Plasma (ICP) sequentially. To determine its mechanical properties, those micropillars are measured by instrument indentation testing (IIT) to obtain its hardness and reduced modulus. For the measurement, a Berkovich diamond indenter is utilized to penetrate a single and also multiple point indentations on a micro-pillar surface. Afterwards, these results are compared to the indentation at the central point of the tested pillar and Si bulk as its reference to examine the influence of different probing locations on the measured reduced modulus and hardness.

Unsteady frequency response of in-plane electro-thermal MEMS-based cantilever sensors can cause up-/down-shifting of the resonance phase, which becomes an inhibitive factor in resonance locking using a phase-locked loop setup. Moreover, the inconsistency of resonance phase during real-time measurement potentially causes inaccuracy in resonant-frequency locking. In this work, reference parameters are differentially subtracted from the sensor output signals to enhance the characteristic of frequency response. As a calculation result, a constant resonance phase can be successfully achieved by adjusting the reference parameters close to the sensor baseline, both in sensor amplitude and phase.

In this paper we present an investigation of the influence of different roughness of etched silicon surfaces on the measured nanomechanical properties. For the etching, inductively coupled plasma (ICP) reactive ion etching (RIE) was performed on the surface of silicon samples with different crystal orientations (i.e., Si , Si , and Si ). Different roughness levels were obtained on each sample by changing the bias voltage through the high-frequency (HF) power. The surface roughness was measured using atomic force microscopy (AFM). The obtained surface roughness for the same etching conditions was different for different crystal orientations. The nanomechanical properties were measured using nanoindentation.

In this paper, a self-reading miniaturized cantilever design for highly sensitive airborne nanoparticle (NP) detection is presented. The cantilever, which is operated in the fundamental in-plane resonance mode, is used as a microbalance with femtogram resolution. For maximum sensitivity and read-out signal amplitude, the geometric parameters of the sensor design were optimized by finite-element modelling (FEM). Piezo-resistive struts at both sides of the cantilever are employed for a Wheatstone half-bridge. This allows the electrical read-out of the phase information of a resonant cantilever of minimum mass. For electrostatic NP collection, the cantilever has a negative-biased electrode located at its free end. Moreover, μ-channels for guiding a particle-laden air flow and a counter-electrode around the cantilever tip are integrated. The presented airborne NP sensor is expected to demonstrate significant improvements in the field of handheld, MEMS-based NP monitoring devices.

Chirped surface acoustic wave (SAW) resonators based on aluminum nitride (AlN) thin films have been designed and fabricated to comprehend the wave propagation characteristics induced by interdigitated transducers (IDTs) deposited on their surfaces. From the simulation results, design and geometry of the metal fingers including their width and pitch play critical roles on the wavelength of the acoustic wave and the mechanical displacement, which subsequently set the device resonant frequency. A single-step metal lift-off process involving photolithography and electron beam metal evaporation has been used to pattern and deposit Cr/Au IDT on AlN-on-Si wafers.

This paper presents a droplet-based method for detecting the mass of fluid-based microparticles. The degree of wettability on silicon-based substrates is therefore investigated for enhanced adsorption of microparticles. Contact angles of 47.3° (pre-treatment) and below 9° (enhanced hydrophilicity upon oxygen plasma treatment) have been realized. Segments of mono-layered particles on the substrate and the possibility of homogenous distribution are also demonstrated. The volume and the surface-contact area of droplets on the substrate have been determined, hence empowering an envisaged optimized design of a particle-well cantilever. The determination of the mass of adsorbed microparticles on the cantilever has also been investigated.

Non-ideal phase responses on electro-thermally actuated piezoresistive cantilever sensors have led the phase-locked loop (PLL) systems into difficulties for real-time sensing applications. These outcomes are caused by thermal-parasitic coupling from the actuating part to the sensing part. Minimizing or eliminating parasitic effects is necessary to obtain an optimized phase response. To realize this, we adjusted the voltage supply of the sensing part, which is in form of a full Wheatstone bridge (WB). By increasing the WB supply voltage (V WB), the phase response can be enhanced. Alternatively, a reference signal that differentially eliminates the parasitic parameter from the sensor output was employed. To investigate the resulting optimized phase response under real-time measurement conditions, two different microcantilevers were connected to an MFLI lock-in amplifier + PLL system (Zurich Instruments). Measurement results exhibited a good sensor performance under varying humidity and temperature conditions.

Vertically aligned gallium nitride (GaN) nanowire (NW) arrays have attracted a lot of attention because of their potential for novel devices in the fields of optoelectronics and nanoelectronics. In this work, GaN NW arrays have been designed and fabricated by combining suitable nanomachining processes including dry and wet etching. After inductively coupled plasma dry reactive ion etching, the GaN NWs are subsequently treated in wet chemical etching using AZ400K developer (i.e., with an activation energy of 0.69 ± 0.02 eV and a Cr mask) to form hexagonal and smooth a-plane sidewalls. Etching experiments using potassium hydroxide (KOH) water solution reveal that the sidewall orientation preference depends on etchant concentration. A model concerning surface bonding configuration on crystallography facets has been proposed to understand the anisotropic wet etching mechanism. Finally, NW array-based vertical field-effect transistors with wrap-gated structure have been fabricated. A device composed of 99 NWs exhibits enhancement mode operation with a threshold voltage of 1.5 V, a superior electrostatic control, and a high current output of >10 mA, which prevail potential applications in next-generation power switches and high-temperature digital circuits.

The asymmetric resonance frequency analysis of silicon cantilevers for a low-cost wearable airborne nanoparticle detector (Cantor) is described in this paper. The cantilevers, which are operated in the fundamental in-plane resonance mode, are used as a mass-sensitive microbalance. They are manufactured out of bulk silicon, containing a full piezoresistive Wheatstone bridge and an integrated thermal heater for reading the measurement output signal and stimulating the in-plane excitation, respectively. To optimize the sensor performance, cantilevers with different cantilever geometries are designed, fabricated and characterized. Besides the resonance frequency, the quality factor (Q) of the resonance curve has a high influence concerning the sensor sensitivity. Because of an asymmetric resonance behaviour, a novel fitting function and method to extract the Q is created, different from that of the simple harmonic oscillator (SHO). For testing the sensor in a long-term frequency analysis, a phase- locked loop (PLL) circuit is employed, yielding a frequency stability of up to 0.753 Hz at an Allan variance of 3.77 × 10-6. This proposed asymmetric resonance frequency analysis method is expected to be further used in the process development of the next-generation Cantor.