SB1341-16-RQ-0844_SOW.docx

STATEMENT OF WORK

TITLE: Procurement of a Pixelated Detector for the Scanning Transmission Electron Microscope (STEM) LAB REQUESTING SERVICE: Material Measurement Laboratory, Materials Measurement Science Division

I. BACKGROUND INFORMATION

The Materials Measurement Science Division (MMSD) of the Material Measurement Laboratory (MML) at the National Institute of Standards and Technology (NIST) is conducting fundamental research in atomic- and nanoscale characterization methods using the scanning transmission electron microscope (STEM). A critical thrust in this research is the development of novel metrology techniques that will provide new capabilities to the scientific and industrial stakeholders in nanoscale science and technology.

In the STEM, a very small (sub-1 nm), high-energy electron beam is scanned over a very thin specimen. Spatially resolved images are produced by serially collecting the transmitted signal generated at each scan position by the interaction of the beam with the specimen. The impinging electrons are scattered in various ways resulting in a rich, two-dimensional scattering distribution which varies as a function of radial and azimuthal position relative to the optic axis of the incoming beam. Ideally, the entire scattering distribution would be collected at each position within the scanned region. However, current detectors do not allow for this to be done at speeds which are practical.

MMSD’s current STEM instrument (FEI Titan 80-300 TEM/STEM) is equipped with two distinct detector classes: single-channel detectors and parallel detectors. The first is capable of collecting all of the electrons which are scattered through a given solid angle at acceptable speeds (typically, around 10 s per image). However, these detectors store only a single integrated intensity value over the collection area, such that all of the angular distribution of the scattered intensity is lost. The pixelated detectors which are currently on the instrument are based on charge-coupled device (CCD) cameras. This latter class consists of a large array of pixels (> 1000 x 1000), which is more than sufficient to detect the full 2D scattering distribution, but can only do so at very slow speeds where a single image would take many minutes to collect. During such a long acquisition, the specimen is exposed to very high levels of radiation which can unacceptably alter or destroy the specimen and environmental and instrumental instabilities are exacerbated. Thus, neither of the existing detectors is adequate for collecting the rich signal generated by the interaction of the beam with the specimen.

This procurement is to obtain a new detector that will allow for collection of a full 2D electron scattering distribution at speeds that are comparable to the existing single-channel detectors. The detection must combine high-speed readout, high detection efficiency, and at least 256 independent multiple detection channels which can be read simultaneously.

II. SCOPE OF WORK

The Contractor shall provide one (1) pixelated STEM detection system consisting of the central detector itself, housing compatible with one of the open detector port on MMSD’s Titan 80-300, and readout electronics for digitizing the signal from all detector channels. The contractor shall also provide shipping and installation of the system. The system shall carry a minimum one-year warranty.

III. SPECIFICATIONS

The contractor shall provide one (1) pixelated STEM detector for MMSD’s Titan 80-300 TEM/STEM.

Format:

The detection system will consist of a square array of detection pixels. At minimum, this array shall be 16x16 pixels in size and the spacing between pixel centers shall be uniform.

Compatibility:

The detection system must be physically compatible with one of the two open high-angle detector ports on MMSD’s STEM instrument. The first port is known as the 35 mm port and is located between the microscope imaging lens system and the microscope viewing chamber, and is positioned opposite a high-angle annular dark-field (HAADF) detector (Fischione Inc.). The second port is positioned below the microscope fluorescent screen and above the entrance to the imaging energy filter. This port currently hosts a multiscan CCD camera (Gatan Inc.). Compatibility is defined by three criteria:

1.) Either the detector must physically fit in the port with no required modification of the instrument or the vendor must supply a compatible flange to enable the addition of the new detector with no loss in other instrument capabilities.

2.) The detector must be properly sealed so that the current performance remains unchanged. The microscope’s projection chamber is pumped by a turbomolecular pump to an operating pressure of 3 x 10-4 Pa. The projection chamber is backed by a scroll pump which runs as needed based on the leak rate of the system. Currently, this interval is approximately 48 hours.

3.) Radiation shielding must not be compromised. The measured radiation dose at and around the detector port must not exceed background levels.

Positioning:

The detector shall be insertable and retractable via either mechanical or pneumatic control. When retracted the detector must be suitably positioned so that no portion of the detector extends beyond the differential pumping aperture which currently defines the maximum scattering angle allowed to pass into the projection chamber. When inserted, the center pixel of the detector should be centered on the optic axis of the microscope.

Interlocks:

If the detector is installed on the 35 mm port, the retraction mechanism shall be interlocked with those controlling the existing HAADF STEM detector (Fischione Model 3000) located on the opposing side of the projection chamber from the designated port. This can be achieved in one of two ways: 1.) software notification of the user to check whether the existing detector is already inserted or 2.) through full integration with the pneumatic system on the microscope. In the latter case, the insertion mechanism of the new, pixelated detector would not function if the existing detector was already inserted. The hardware integration is the preferred option, however, if cost or engineering difficulty prevents it, the software option will be sufficient.

Performance:

All pixels in the detector array must achieve the following minimum requirements:

Quantum efficiency: The detective quantum efficiency (DQE) must exceed 0.9.

Readout: All detector pixels must be readout simultaneously during a given imaging experiment. The readout rate for the entire array must meet or exceed a frequency of 1 kHz.

Dynamic range: The detector shall exhibit a dynamic range of at least 12 bit.

Durability: The detector must be resistant to degradation due to exposure to the high energy electron beam in the microscope. The instrument operates using electron energies from 60 keV to 300 keV, and probe currents typically used for imaging experiments fall between 30 pA and 100 pA.

Cross-talk: Cross-talk is defined as the change in signal output from all other detector elements when the electron beam is impinging on only a single element. This value shall not exceed the noise level of the detector elements.

Noise level: The standard deviation of each detector element output shall be less than 1 % as measured from a series of 100 images collected in series when no specimen is in the field of view.

Dark-current: The mean current readout from each pixel over a 10 second period of time shall not exceed 0.1 % of the saturation level when no electron illumination is present.

Signal processing:

The contractor shall provide the necessary electronics to digitize the output signal from the detector and to store the data for subsequent processing. The data must be stored in an open format to enable custom data processing approaches.

Installation:

Upon delivery of the detection system, the contractor shall provide personnel and equipment necessary to install the detector on MMSD’s STEM instrument. This shall include all associated labor and travel costs, as well as a period of testing sufficient to demonstrate that the system meets all of the required specifications.

Warranty:

The Contractor shall provide, at a minimum, a one-year warranty for the equipment. The warranty shall cover all parts, labor, and travel. The warranty shall commence upon successful completion of delivery, installation, training and demonstration of all required specifications.

IV. PERIOD OF PERFORMANCE

The period of performance shall include the time necessary for detector design and fabrication as well as one (1) year of warranty after delivery and acceptance.

V. DELIVERABLES

The contractor shall deliver the equipment FOB Destination terms to:

The National Institute of Standards and Technology 100 Bureau Drive Gaithersburg, MD 20899

VI. GENERAL INFORMATION

Quote Instructions: The contractor shall disclose the overall design of the detector to the NIST TPOC prior to award. This disclosure may be covered by a non-disclosure agreement.