Variable Pressure Scanning Electron Microscope – Hitachi S3200N

The Hitachi S3200N variable pressure scanning electron microscope (VPSEM) is a conventional high resolution thermionic SEM, which allows the operator to control the specimen chamber vacuum level.

For conductive samples, the instrument is typically operated in high vacuum mode and images are collected with the Everhart-Thornley secondary electron detector. For insulating samples, the instrument is typically operated in variable pressure mode and images are collected with the Robinson backscattered electron detector. When operating in variable pressure mode, the chamber is back filled with a gas in order to allow imaging with little or no charging of the sample. Typically, the back fill gas is either N2 or He, but any non-corrosive, non-reactive gas can be used. Elemental analysis using the energy dispersive X-ray detector can be done in either high vacuum or variable pressure mode.

The Hitachi S3200N SEM is equipped with the standard Everhard-Thornley secondary electron detector, a Robinson backscattered electron detector, an Oxford energy dispersive X-ray spectrometer, and a GW specimen current meter. Electrical feedthroughs are also mounted on the chamber to allow powering active electrical devices or observing electron beam induced current (EBIC). A 4Pi Universal Spectral Engine (electronics set) allows for digital data collection from all of the detectors.

Questions? Contact Chuck Mooney at cbmooney@ncsu.edu.
Location: MRC room 321

Equipment Specifications

Detectors	Everhart-Thornley secondary electron detector Robinson backscattered electron detector Oxford energy dispersive X-ray spectrometer GW Specimen current meter GW ChamberScope
Capabilities	Digital imaging of secondary electron images (topographical contrast) Digital imaging of backscattered electron images (atomic number contrast) Digital collection of X-ray spectra Digital X-ray mapping Digital imaging of specimen current EBIC (assumes a means of electrically connecting to the sample!)
Accelerating Voltage	0.3 – 30 kV
Magnification	20X – 300,000X
Resolution (SE)	3.5 nm @ 30kV in high vacuum mode using the secondary electron detector
Resolution (BSE)	5.5 nm @ 30kV in variable pressure mode using the backscattered electron detector
Working Distance	3-60 mm
Specimen Stage	Eucentric tilt -20º to +90º Rotate 360º x = 60 mm y = 40 mm z = 26 mm
Specimen Considerations	Accepts most samples: Conductors, Semiconductors, and Insulators can be observed Including, but not limited to metals, semiconductor devices, ceramics, biological, polymer, textile, pharmaceuticals, even food, etc. Specimens can be up to 150mm in diameter and up to 40mm thick Only the center 60x40mm area can be observed on large specimens

Documentation

Hitachi3200 Operating Instructions

Images

Example Analysis: EDS spectrum of the darkest part of the dark sphere showing that this region is mostly C.

Sand Dollar (found at an NC beach) observed with the Robinson BSE detector at 500X.

Dendritic growth of Ag from a colloidal suspension observed with the Everhart-Thornley SE detector.

Etched Pearlite. Sample courtesy Lew Reynolds.

Pyrite (FeS) “framboids” filling the shell of a foraminifera in sediments from the continental shelf seaward of the North Island, New Zealand. Pyrite forms under reducing conditions in shallowly buried, organic-rich marine sediments.
From the work of Lonnie Leithold.

Lead-tin eutectic imaged with Robinson BSE detector. The BSE detector is sensitive primarily to changes in atomic number with higher atomic number materials having more contrast. In this case, the Pb is brightest and the Sn is darker. The dark particles observed are polishing media that are embedded in the sample. Sample courtesy Lew Reynolds.

Pollen sample taken from AIF staff member Chuck Mooney’s car.