Development of multi-depth probing 3D microelectrode array to record electrophysiological activity within neural cultures

Microelectrode arrays (MEAs) play a crucial role in investigating the electrophysiological activities of neuronal populations. Although two-dimensional neuronal cell cultures have predominated in neurophysiology in monitoring in-vitro the electrophysiological activity, recent research shifted toward culture using three-dimensional (3D) neuronal network structures for developing more sophisticated and realistic neuronal models. Nevertheless, many challenges remain in the electrophysiological analysis of 3D neuron cultures, among them the development of robust platforms for investigating the electrophysiological signal at multiple depths of the 3D neurons' networks. While various 3D MEAs have been developed to probe specific depths within the layered nervous system, the fabrication of microelectrodes with different heights, capable of probing neural activity from the surface as well as from the different layers within the neural construct, remains challenging. This study presents a novel 3D MEA with microelectrodes of different heights, realized through a multi-stage mold-assisted electrodeposition process. Our pioneering platform allows meticulous control over the height of individual microelectrodes as well as the array topology, paving the way for the fabrication of 3D MEAs consisting of electrodes with multiple heights that could be tailored for specific applications and experiments. The device performance was characterized by measuring electrochemical impedance, and noise, and capturing spontaneous electrophysiological activity from neurospheroids derived from human induced pluripotent stem cells. These evaluations unequivocally validated the significant potential of our innovative multi-height 3D MEA as an avant-garde platform for in vitro 3D neuronal studies

Fabrication of a Highly NO2-Sensitive Gas Sensor Based on a Defective ZnO Nanofilm and Using Electron Beam Lithography

Hazardous substances produced by anthropic activities threaten human health and the green environment. Gas sensors, especially those based on metal oxides, are widely used to monitor toxic gases with low cost and efficient performance. In this study, electron beam lithography with two-step exposure was used to minimize the geometries of the gas sensor hotplate to a submicron size in order to reduce the power consumption, reaching 100 °C with 0.09 W. The sensing capabilities of the ZnO nanofilm against NO2 were optimized by introducing an enrichment of oxygen vacancies through N2 calcination at 650 °C. The presence of oxygen vacancies was proven using EDX and XPS. It was found that oxygen vacancies did not significantly change the crystallographic structure of ZnO, but they significantly improved the electrical conductivity and sensing behaviors of ZnO film toward 5 ppm of dry air

Imaging of Antiferroelectric Dark Modes in an Inverted Plasmonic Lattice [Dataset]

6 pages. -- S1. Transversal electric field distribution for the SLR at 1.57 eV. -- S2. Simulated electric field and charge distributions for a threesome of slits. -- S3. Simulated electric field and charge distributions for the simplest local dark mode of the inverted honeycomb lattice. -- S4. Profiles of the EELS signal and the simulated electric field along the slits for the antiferroelectric dark modes. -- S5. Array of the magnetic dipoles over the structure used to simulate antiferroelectric dark modes.Plasmonic lattice nanostructures are of technological interest because of their capacity to manipulate light below the diffraction limit. Here, we present a detailed study of dark and bright modes in the visible and near-infrared energy regime of an inverted plasmonic honeycomb lattice by a combination of Au+ focused ion beam lithography with nanometric resolution, optical and electron spectroscopy, and finite-difference time-domain simulations. The lattice consists of slits carved in a gold thin film, exhibiting hotspots and a set of bright and dark modes. We proposed that some of the dark modes detected by electron energy-loss spectroscopy are caused by antiferroelectric arrangements of the slit polarizations with two times the size of the hexagonal unit cell. The plasmonic resonances take place within the 0.5–2 eV energy range, indicating that they could be suitable for a synergistic coupling with excitons in two-dimensional transition metal dichalcogenides materials or for designing nanoscale sensing platforms based on near-field enhancement over a metallic surface.Peer reviewe

Optimization of secondary ion mass spectrometry ultra-shallow boron profiles using an oblique incidence O2+ beam

The features of ultra-shallow junctions indicated by 2001 International Roadmaps require challenging characteristics for secondary ion mass spectrometry (SIMS) instruments: an ultra high depth resolution, minimization of transient width before the steady state and the ability to manage high concentration quantification in the near surface region. In this article a new magnetic sector SIMS, the Cameca Sc-Ultra, has been evaluated in order to profile boron ultra shallow junctions. In this apparatus the use of normal incidence oxygen bombardment is precluded and the primary column allows for a 60° nominal incidence angle. Several approaches varying analytical parameters as energy, incidence angle and oxygen flooding have been tested on boron delta layers samples. In this way a quantitative comparison of different analytical methodologies is possible and the better analytical approach is pointed out. Moreover, an in situ laser depth profile measurement tool has been tested and the advantages and limitation are shown. The minimum impact energy used is 0.5 keV, but the instrument performance can be further improved by using lower impact energy (300 eV), a rotating stage to minimize surface roughness, and a primary column with a nominal angle of 30°. SIMS depth profiles on technological samples have been also carried out and show

Preface for Proceedings of SIMS XVIII, Riva del Garda, Italy, 2011

No abstract is available for this article

GIXRF In The Soft X-Ray Range Used For The Characterization Of Ultra Shallow Junctions

Grazing Incidence X-Ray Fluorescence (GIXRF) analysis in the soft X-ray range provides excellent conditions for exciting B-K and As-Liii,ii shells. The X-ray Standing Wave field (XSW) associated with GIXRF on flat samples is used as a tunable sensor to gain information about the implantation profile in the nm range due to the in-depth changes of the XSW intensity dependent on the angle between the sample surface and the primary beam. This technique is very sensitive to near surface layers. It is therefore well suited for the study of ultra shallow dopant distributions. Arsenic implanted (100) Si wafers with nominal fluence between 1.0E14 cm−2 and 5.0E15 cm−2 and implantation energies between 0.5 keV and 5.0 keV and Boron implanted (100) Si wafers with nominal fluence of 1.0E14 cm−2 and 5.0E15 cm−2 and implantation energies between 0.2 keV and 3.0 keV have been used to compare SIMS analysis with synchrotron radiation induced GIXRF analysis in the soft X-ray range. The measurements have been carried out at the laboratory of the Physikalisch-Technische Bundesanstalt at the electron storage ring BESSY II using monochromatized undulator radiation of well-known radiant power and spectral purity. Here the use of an absolutely calibrated energy-dispersive detector for the registration of the B-K and As-L fluorescence radiation allows for the absolute determination of the total retained dose. An estimate of the concentration profile has been obtained by fitting the X-ray fluorescence angular scans with profiles derived by simulation of the implantation process. A good match among the total retained dose measured with the different techniques has been observed

Enhancing the Deposition Rate and Uniformity in 3D Gold Microelectrode Arrays via Ultrasonic-Enhanced Template-Assisted Electrodeposition

In the pursuit of refining the fabrication of three-dimensional (3D) microelectrode arrays (MEAs), this study investigates the application of ultrasonic vibrations in template-assisted electrodeposition. This was driven by the need to overcome limitations in the deposition rate and the height uniformity of microstructures developed using conventional electrodeposition methods, particularly in the field of in vitro electrophysiological investigations. This study employs a template-assisted electrodeposition approach coupled with ultrasonic vibrations to enhance the deposition process. The method involves utilizing a polymeric hard mask to define the shape of electrodeposited microstructures (i.e., micro-pillars). The results show that the integration of ultrasonic vibrations significantly increases the deposition rate by up to 5 times and substantially improves the uniformity in 3D MEAs. The key conclusion drawn is that ultrasonic-enhanced template-assisted electrodeposition emerges as a powerful technique and enables the development of 3D MEAs at a higher rate and with a superior uniformity. This advancement holds promising implications for the precision of selective electrodeposition applications and signifies a significant stride in developing micro- and nanofabrication methodologies for biomedical applications

Visita ispettiva annuale di sorveglianza Accredia

ispettiva di sorveglianza 5-6 maggio 2011. L'accreditamento dura 4 anni ma deve essere rinnovato ogni anno.

Ultra Shallow Depth Profiling by Secondary Ion Mass Spectrometry Techniques

Ultra shallow dopant profiles are one of the major challenges for ULSI silicon metrology. Following the ITRS 2002, the 90nm technology node will appear in 2004 along with the maximum drain extension in the range of 15-25 nm for both P-MOS and N-MOS devices. In this frame, a very abrupt junction with a decay lenght of 4 nm/decade is mandatory. A depth resolution better than 0.7 nm in profiling shallow implanted dopants is consequently required. In this review, after a brief summary on necessities and difficulties of (N-MOS)ultra shallow profiling for the 90 nm technology node, we present a comparison between two Secondary Ion Mass Spectrometry (SIMS) approaches using different instruments (Magnetic Sector and Time of Flight Spectrometers) for the characterization of arsenic ultra shallow profiles. A particular relevance is dedicated to the methodological optimization and data processing, mainly in quantification and depth scale determination. Quantitative SIMS results have been compared with complementary techniques like LEXES, MEIS and RB

Development of nano-topography during SIMS characterization of Ge1-xSnx alloy

none5Ge1-xSnx is a semiconductor alloy, compatible with silicon technology, with a bandgap tunable with Sn concentration (3%<x<7% can change the Ge bandgap from indirect to direct) [1], high electron and hole mobility [2,3]. For all those applications, it is mandatory to define analytical approaches able to provide accurate measurements of Sn content. SIMS can be a valuable choice but quantification and matrix issues due to the high Sn content need to be addressed. Therefore, we developed a SIMS protocol using Sn ion implants on Ge as reference samples. Ion implantation was carried out at liquid nitrogen temperature, in order to avoid the well-known phenomenon of Ge nanostructuration under heavy ion implantation at room temperature [4,5]. Implant fluences varied between 1x10^14 at/cm2 and 5x10^15 at/cm2 and implant energy was set at 45keV. SIMS characterization was performed in different configurations, i.e. using O2+ as primary beam and collecting positive secondary ions, Cs+ and negative secondary ions, Cs+ collecting MCs+ ions; the final results were compared with quantitative measurements obtained by RBS, revealing a good accuracy for the MCs+ protocol. However, it was observed that the applied sputtering conditions (Cs+ 1 keV, 55° incidence vs. normal) induced an early formation of surface topography resulting in a variation of sputtering yield. AFM images will be reported showing the peculiar topography developed on Ge and corrections to improve depth calibration accuracy will be discussed. The obtained protocol was then used to quantify also SIMS profiles of room temperature Sn implants, i.e. nanostructured Ge samples, with good accuracy. [1] S. Gupta et al., IEDM 2011. [2] G. He and H.A. Atwater, Phys. Rev. Lett., 79, (2007), 1937. [3] J.D. Sau and M.L. Cohen, Phys. Rev. B, 75, (2007), 045208. [4] I.H. Wilson, J. Appl. Phys. 53(3), (1982), 1698. [5] N.G. Rudawski and K.C. Jones, J. Mater. Res. 28(13), 1633, 2013M. Secchi; E. Demenev; D. Giubertoni; E. Iacob; M. BersaniM. Secchi; E. Demenev; D. Giubertoni; E. Iacob; M. Bersan