a-procedure-for-implanting-organized-arrays-microwires-for-single

A Procedure for Implanting Organized Arrays of Microwires for Single-unit Recordings in Awake, Behaving Animals

In vivo electrophysiological recordings in the awake, behaving animal provide a powerful method for understanding neural signaling at the single-cell ...

building-an-open-source-robotic-stereotaxic-instrument

Building An Open-source Robotic Stereotaxic Instrument

This protocol includes the designs and software necessary to upgrade an existing stereotaxic instrument to a robotic (CNC) stereotaxic instrument for ...

Rutgers, the State University of New Jersey

A modified back-etch method is described that has been successfully used to prepare samples of thin films and nanoparticles on Si wafer substrates for examination by high-resolution transmission electron microscopy (HRTEM). This process includes ultrasonic cutting, abrasive pre-thinning and a two-stage etching procedure. Unlike previous reports of back-etching methods, tetramethyl ammonium hydroxide, which has a very high-etching selectivity of Si to SiO(2), is used for the final etching to allow removal of the Si without degradation of the SiO(2) membrane. An innovative wrapping method is also described. This novel approach reduces the preparation time for HRTEM samples to <1 h per sample for groups of 10 or more samples. As an example, the preparation of FePt nanoparticle samples for HRTEM imaging is described.

A modified back-etch method for preparation of plan-view high-resolution transmission electron microscopy samples.

Back-etch methods have been widely used to prepare plan view transmission electron microscopy (TEM) samples of thin films on membranes by removal of the Si substrate below the membrane by backside etching. The conventional means to determine when to stop the etch process is to observe the color of the light transmitted through the sample, which is sensitive to the remaining Si thickness. However, most metallic films thicker than 75 nm are opaque, and there is no detectable color change prior to film perforation. In this paper, a back-etch method based on the observation of an abrupt change of optical reflection contrast is introduced as a means to determine the etch endpoint to prepare TEM samples for these films. As the acid etchant removes the Si substrate material a rough interface is generated. This interface becomes a relatively smooth and featureless region when the etchant reaches the membrane (film/SiO2). This featureless region is caused by the mirror reflection of the film plane (film/SiO2 interface) through the optically transparent SiO2 layer. The lower etch rate of SiO2 (compared with Si) gives the operator enough time to stop the etching without perforating the film. A clear view of the morphology and control of Si roughness during etching are critical to this method, which are discussed in detail. The procedures of mounting wax removal and sample rinsing are also described in detail, as during these steps damage to the membrane may easily occur without appropriate consideration. As examples, the preparation of 100-nm-thick Fe-based amorphous alloy thin film and 160-nm-thick Cu-thin film samples for TEM imaging is described.

Back-etch method for plan view transmission electron microscopy sample preparation of optically opaque films.

Cross-sectional transmission electron microscopy (XTEM) is a very useful technique to study the interfacial diffusion and reactions and the grain growth of thin films. However, the preparation of XTEM samples of thin films is tedious and challenging. Difficulties may include the delamination of films from the substrate, fracture of brittle substrates and differential milling rates of the substrate and the film. This paper describes an improved technique using a combination of tripod polishing and focused ion beam milling to prepare XTEM samples of thin films. The technique can be widely used for high-throughput production of samples having varying film and substrate properties. Two different geometries are introduced. The first one is suitable for XTEM sample preparation of most films at a high yield rate, but with a limited view area. The other geometry is able to give a larger view area and is more suitable for thicker films. The technique is illustrated by an example of the sample preparation of Fe/Pt multilayer films on SiO2/Si substrates.

A high-throughput approach for cross-sectional transmission electron microscopy sample preparation of thin films.

In this paper, we describe hollow-cone dark field (HCDF) transmission electron microscopy (TEM) imaging, with a slightly convergent beam, as an improved technique that is suitable to form high contrast micrographs for nanocrystalline grain size quantification. We also examine the various factors that influence the HCDF TEM image quality, including the conditions of microscopy (alignment, focus and objective aperture size), the properties of the materials imaged (e.g., atomic number, strain, defects), and the characteristics of the TEM sample itself (e.g., thickness, ion milling artifacts). Sample preparation was found to be critical and an initial thinning by wet etching of the substrate (for thin film samples) or tripod polishing (for bulk samples), followed by low-angle ion milling was found to be the preferred approach for preparing high-quality electron transparent samples for HCDF imaging.

High contrast hollow-cone dark field transmission electron microscopy for nanocrystalline grain size quantification.

It has been proposed that cocaine abuse results in skilled or "automatic" drug-taking behaviors. Brain regions important for skill learning are implicated in cocaine self-administration. However, the development of skill during self-administration has not been investigated.

Evidence for learned skill during cocaine self-administration in rats.

Long Evans rats (n=32) were trained for 2 weeks to respond to an auditory conditioned stimulus (CS) which signaled the delivery of a 20% sucrose unconditioned stimulus (US) with varying probabilities. Animals were randomly assigned to 1 of 4 groups. In the control groups, the CS signaled sucrose delivery with equal probabilities across two weeks, at 100% (Group 100-100) and 25% (Group 25-25) respectively. In the experimental groups (Group 100-25) and (Group 25-100), sucrose probabilities were switched between weeks 1 and 2. Three behavioral measures were recorded: latency to enter the sucrose port upon CS presentation, head entries throughout the session and ultrasonic vocalizations. The results suggest that all groups formed associations between the CS and US, as evidenced by a decrease in latency to respond to the CS across days. The experimental groups were also able to detect when sucrose probability changed, as evidenced by Group 25-100's increase in head entries, to the level of Group 100-100 in week 2, and Group 100-25's decrease in head entries, to the level of Group 25-25 in week 2. Group 100-25 also produced an increase in "22 kHz" ultrasonic vocalizations following the downshift on the first day of week 2. The increase in this ultrasonic frequency range, which is associated with negative affect in rats, preceded both the decrease in head entries and the increase in missed trials, consistent with a multistage model of behaviors resulting from US probability reduction.

Effects of varying reinforcement probability on pavlovian approach behavior and ultrasonic vocalizations in rats.

This work demonstrates an anisotropic increase in resistivity with decreasing width in single crystal tungsten (W) nanowires having a height of 21 nm. Nanowire-widths were in the range of 15-451 nm, with the anisotropy observed for widths below 50 nm. The longitudinal directions of the nanowires coincided with the <100>, <110> and <111> orientations of the body centered cubic phase of W. The resistivity increase was observed to be minimized for the <111>-oriented single crystal nanowires, exhibiting a factor of two lower increase in resistivity at a width of ~15 nm, relative to the thin film resistivity (i.e., an infinitely wide wire). The observed anisotropy is attributed to crystallographic anisotropy of the Fermi velocity and the resultant anisotropy of the electron mean free path in W, and underscores the critical role of crystallographic orientation in nanoscale metallic conduction.

ArticleTotal : 2	Year
Publication title Cited by 7	2014
Publication title Cited by 17	2013

Article	Year
A modified back-etch method for preparation of plan-view high-resolution transmission electron microscopy samples. Journal of electron microscopy\| PubMed ID: 17040930	2006
Back-etch method for plan view transmission electron microscopy sample preparation of optically opaque films. Journal of electron microscopy\| PubMed ID: 18227137	2008
A high-throughput approach for cross-sectional transmission electron microscopy sample preparation of thin films. Journal of electron microscopy\| PubMed ID: 18984643	2008
High contrast hollow-cone dark field transmission electron microscopy for nanocrystalline grain size quantification. Micron (Oxford, England : 1993)\| PubMed ID: 20018512	2010
Evidence for learned skill during cocaine self-administration in rats. Psychopharmacology\| PubMed ID: 21455708	2011
Effects of varying reinforcement probability on pavlovian approach behavior and ultrasonic vocalizations in rats. Behavioural brain research\| PubMed ID: 23022752	2013
Crystallographic anisotropy of the resistivity size effect in single crystal tungsten nanowires. Scientific reports\| PubMed ID: 24005230	2013

Kevin R. Coffey

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