Quantitative scanning spreading resistance microscopy on n-type dopant diffusion profiles in germanium and the origin of dopant deactivation

Diffusion profiles of arsenic and antimony in undoped and carbon doped germanium (Ge), respectively, were analysed by means of scanning spreading resistance microscopy (SSRM). Whereas earlier secondary ion mass spectrometry analyses have determined the distribution of the chemical concentration of dopants and carbon, the electrically active defect concentration is quantified by SSRM using appropriate calibration samples and a preparation technique that reduces the surface roughness and its density of electronic states. Pronounced differences between the chemical and electrical dopant profiles are observed and consistently described by the formation of inactive dopant defect complexes in the framework of the vacancy mediated diffusion of donor atoms in Ge. This reveals that donor deactivation occurs during dopant diffusion at elevated temperatures

Design of Miniaturized, Self-Out-Readable Cantilever Resonator for Highly Sensitive Airborne Nanoparticle Detection

In this paper, a self-out-readable, miniaturized cantilever resonator 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. To achieve a maximum measurement signal of the piezo resistive Wheatstone half-bridge, the geometric parameters of the sensor design were optimized by finite element modelling (FEM). Struts at the sides of the cantilever resonator act as piezo resistors and enable an electrical read-out of the phase information of the cantilever movement whereby they do not contribute to the resonators rest mass. For the optimized design, a resonator mass of 0.93 ng, a resonance frequency of ~440 kHz, and thus a theoretical sensitivity of 4.23 fg/Hz can be achieved. A μ-channel guiding a particle-laden air flow towards the cantilever is integrated into the sensor chip. Electrically charged NPs will be collected by an electrostatic field between the cantilever and a counter-electrode at the edges of the μ-channel. Such μ-channels will also be used to accomplish particle separation for sizeselective NP detection. Throughout, the presented airborne NP sensor is expected to demonstrate significant improvements in the field of handheld, MEMS-based NP monitoring devices

Design of Miniaturized, Self-Out-Readable Cantilever Resonator for Highly Sensitive Airborne Nanoparticle Detection

In this paper, a self-out-readable, miniaturized cantilever resonator 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. To achieve a maximum measurement signal of the piezo resistive Wheatstone half-bridge, the geometric parameters of the sensor design were optimized by finite element modelling (FEM). Struts at the sides of the cantilever resonator act as piezo resistors and enable an electrical read-out of the phase information of the cantilever movement whereby they do not contribute to the resonators rest mass. For the optimized design, a resonator mass of 0.93 ng, a resonance frequency of ~440 kHz, and thus a theoretical sensitivity of 4.23 fg/Hz can be achieved. A μ-channel guiding a particle-laden air flow towards the cantilever is integrated into the sensor chip. Electrically charged NPs will be collected by an electrostatic field between the cantilever and a counter-electrode at the edges of the μ-channel. Such μ-channels will also be used to accomplish particle separation for sizeselective NP detection. Throughout, the presented airborne NP sensor is expected to demonstrate significant improvements in the field of handheld, MEMS-based NP monitoring devices

Fabrication of ZnO Nanorods on MEMS Piezoresistive Silicon Microcantilevers for Environmental Monitoring

In this study, a ZnO nanorods (NRs) patterned MEMS piezoresistive silicon micro-cantilever was fabricated as environmental monitor. The fabrication starts from bulk silicon, utilizing photolithography, diffusion, inductively coupled plasma (ICP) cryogenic dry etching, Zinc DC-sputtering, and chemical bath deposition (CBD) etc. This sensor shows a humidity sensitivity value of 6.35 ± 0.27 ppm/RH% at 25 °C in the range from 30% RH to 80% RH

Transferable micromachined piezoresistive force sensor with integrated double-meander-spring system

A developed transferable micro force sensor was evaluated by comparing its response with an industrially manufactured device. In order to pre-identify sensor properties, three-dimensional (3-D) sensor models were simulated with a vertically applied force up to 1000 µN. Then, controllable batch fabrication was performed by alternately utilizing inductively coupled plasma (ICP) reactive ion etching (RIE) and photolithography. The assessments of sensor performance were based on sensor linearity, stiffness and sensitivity. Analysis of the device properties revealed that combination of a modest stiffness value (i.e., (8.19 ± 0.07) N m−1) and high sensitivity (i.e., (15.34 ± 0.14) V N−1) at different probing position can be realized using a meander-spring configuration. Furthermore, lower noise voltage is obtained using a double-layer silicon on insulator (DL-SOI) as basic material to ensure high reliability and an excellent performance of the sensor

Piezo Resistive Read-Out Contact Resonance Spectroscopy for Material and Layer Analysis at High-Aspect-Ratio Geometries

A piezo resistive, phase locked loop (PLL) controlled micro tactile measurement system for contact resonance spectroscopy (CRS) at high-aspect-ratio geometries was developed and characterised. Therefore, a piezo resistive silicon cantilever with a silicon tip at its free end was brought into contact with a sample surface and excited into resonance by a piezo actuator. The resonance frequency of the contacted cantilever was tracked by a homemade closed-loop PLL circuit. Different materials and layer thicknesses of photo resist (PR) on silicon were used to validate the system. To optimise the sensitivity and efficiency of the measurement system, amplitude and phase of the cantilever in surface contact were analysed under different contact forces and excitation amplitudes

Nanomechanical Traceable Metrology of Vertically Aligned Silicon and Germanium Nanowires by Nanoindentation

Silicon and germanium pillar structures (i.e., micro- and nanowires) were fabricated by a top-down approach including nanoimprint lithography and cryogenic dry etching. Various etching parameters were tested to ensure a reliable fabrication process. The impression of nanomechanical properties of such 3-D structures were extracted experimentally by nanoindentation showing promising and comparative results to utilize such nanostructures as small force artefacts

Nanomechanical Characterization of Vertical Nanopillars Using an MEMS-SPM Nano-Bending Testing Platform

Nanomechanical characterization of vertically aligned micro- and nanopillars plays an important role in quality control of pillar-based sensors and devices. A microelectromechanical system based scanning probe microscope (MEMS-SPM) has been developed for quantitative measurement of the bending stiffness of micro- and nanopillars with high aspect ratios. The MEMS-SPM exhibits large in-plane displacement with subnanometric resolution and medium probing force beyond 100 micro-Newtons. A proof-of-principle experimental setup using an MEMS-SPM prototype has been built to experimentally determine the in-plane bending stiffness of silicon nanopillars with an aspect ratio higher than 10. Comparison between the experimental results and the analytical and FEM evaluation has been demonstrated. Measurement uncertainty analysis indicates that this nano-bending system is able to determine the pillar bending stiffness with an uncertainty better than 5%, provided that the pillars’ stiffness is close to the suspending stiffness of the MEMS-SPM. The MEMS-SPM measurement setup is capable of on-chip quantitative nanomechanical characterization of pillar-like nano-objects fabricated out of different materials

Towards fabrication of 3D isotopically modulated vertical silicon nanowires in selective areas by nanosphere lithography

International audienceAn improved nanofabrication processing technique for realization of vertically aligned silicon nanowires (SiNW5) by colloidal lithography is reported in this work. Microstructure pattern arrays are prepared on the substrate allowing selective deposition of polystyrene (PS) nanoparticles. Using PSS/PDDA/PSS-layer, surface properties can be modified resulting in an enhanced hydrophilicity of the silicon substrate, which is followed by high surface coverage up to-83% after particle transfer. During the fabrication, we demonstrate full control of the mask dimension providing excellent control of nanostructure feature size by inductively coupled plasma (ICP) reactive ion etching (RIE) process at cryogenic temperature. Finally, this combined approach of bottom-up and top-down methods offers simple and direct nanoscale processing steps with low-cost and great reproducibility, enabling high density fabrication of nanostructure (similar to 10(9) SiNW/cm(2)) within certain area. This preparation route of the SiNWs was applied to isotopically controlled silicon layers grown epitaxially on Si substrates. Atom probe tomography of these SiNWs reveal that the isotope layer ordering is preserved by the NW fabrication route. (C) 2017 Elsevier B.V. All rights reserved