Surface Analysis Center

The X-ray photoelectron spectroscopy facility in the chemistry department houses a high sensitivity Kratos AXIS 165 spectrometer. This state-of-the-art instrument is a high performance spectrometer with imaging capabilities and is designed to meet the demanding needs of surface scientists.

Technique

XPS_PHYSICS

X-ray photoelectron spectroscopy is a widely used method of determining the chemical composition of a surface. The analysis is done by irradiating a sample with soft x-rays to ionize atoms and releasing core-level photoelectrons. The kinetic energy of the escaping photoelectrons limits the depth from which it can emerge, giving XPS its high surface sensitivity and sampling depth of a few nanometers. Photoelectrons are collected and analyzed by the instrument to produce a spectrum of emission intensity versus electron binding energy. Since each element has a unique set of binding energies, XPS can be used to identify the elements on the surface. Also, peak areas at nominal binding energies can be used to quantify concentration of the elements. Small shifts in these binding energies (chemical shifts) provide powerful information about sample chemical states and short-range chemistry. XPS is suitable for the analysis of both conductors and insulators.

This facility has been supported by the National Science Foundation and the Materials Research Science and Engineering Center (MRSEC) since 2003 and is available for collaborative research projects.

Instrumentation

Key features of the instrument are:

  • 165 mm radius hemispherical analyzer and eight channeltron detection system for excellent energy resolution and sensitivity for small areas
  • Magnetic immersion lens for superior sensitivity for small area analysis and imaging
  • Charge neutralization system for insulating samples
  • Variable temperature sample stage (150-750 K) for temperature controlled measurements
  • Capable of XPS imaging and multipoint spectroscopy
  • Depth profiling with argon ion bombardment
  • Automated sample stage and XYZ manipulator for angle resolved measurements
  • Two x-ray sources: Monochromatic Al and Dual anode (Mg/Al)
  • Fully computer controlled system with windows based Vision software.

XPS Analysis Requests

Download XPS Analysis Request Form (pdf format)

XPS Request Form – External

Sample Requirements

Contact

For general questions about XPS, the capabilities of the facility and sample analysis strategies or to schedule an appointment contact:

Dr. Karen Gaskell
Department of Chemistry & Biochemistry
University of Maryland, College Park, MD 20742
Phone 301.405.4999 Fax 301.314.9121

The surface analysis center houses a state-of-the-art atomic force microscope (AFM) capable of meeting the AFM needs of most researchers. The lab has a Veeco Multimode AFM with a Nanoscope III controller, 180×180 micron scanner and Nanoscope Version 5.3 software. The instrument is available for students and post-doctoral researchers to use after the training.

Technique

AFMsetup

Atomic Force Microscopy (AFM) is a form of scanning probe microscopy (SPM) that is used to image the surface of a specimen using a cantilever for morphological studies. The cantilever has a sharp tip with a radius curvature. As the tip is brought down close to the sample surface, the tip interacts with the sample surface leading to either repulsive forces (contact mode AFM) or attractive forces (tapping mode AFM). In contact mode AFM, where the tip is very close to the surface, the repulsive forces are used to image the surface. In tapping mode AFM, the tip is oscillated at a resonant frequency and tip sample height is much farther away than in contact mode AFM. The image in tapping mode AFM is obtained from the the attractive forces between the tip and the sample.

This Facility has been supported by the National Science Foundation and the Materials Research Science and Engineering Center (MRSEC) since 2003 and is available for collaborative research projects.

Instrument

IMG_0175

Capabilities

  • Contact mode
  • Tapping Mode
  • Lateral Force
  • Liquid Phase Imaging

AFM probes/supplies available in facility at cost price

  • SiN contact probe (<15 nm tip radius)
    4 cantilevers / Au-Cr coated
  • Si Contact probe (< 10 nm tip radius)
    1 cantilever / Au coated
  • Si tapping probe (< 10 nm tip radius)
    1 cantilever / Au coated
  • 15 mm Specimen discs
  • 12 mm glass sample mount
  • 9.9 mm mica discs (interleafed)
  • Gel-pak box for storing probes

Becoming a user of the AFM

1. Schedule training

  • Basic Training: Standard operation of the microscope in either tapping or contact mode is covered in detail. During the supervised training, users are taught to image using a standard calibration grid. The AFM training takes around 3 hours. Users are strongly recommended to practice immediately after the training.
  • Advanced Training: A number of techniques can be covered in the advanced training, including: lateral force microscopy (LFT), force curve measurements and liquid imaging. At least 5 hours must be logged on the instrument before advanced training may be taken.

2. Complete one of the following forms and return to SAC

3. Register on the NanoCenter website – once trained you will be able to sign-up for time

Signup calendar
Click on register to create login

Rules for using the AFM

1. Only authorized users (users after training) are permitted to use the instrument.
2. Users of the instrument are expected to keep the instrument neat and tidy.
3. Users are NOT permitted to disconnect connections or remove parts. If the user needs to make changes to the standard instrument setup, they need to contact Dr. Karen Gaskell.
4. Users are required to make a reservation if they need to use the instrument. Users are NOT permitted to use the instrument without a reservation.
5. Users are not permitted to use the instrument beyond the reserved time without extending their reservations, provided there is no one else reserved.
6. If you have made a reservation to use the instrument and if another user is occupying the instrument, you have the right to ask them to leave.
7. If you have any questions or concerns regarding these rules, please see Dr. Karen Gaskell.

Contact

Dr. Karen Gaskell
Department of Chemistry & Biochemistry
University of Maryland, College Park, MD 20742
Phone 301.405.4999 Fax 301.314.9121

Useful Links

Sample Requirements

Standard Operating Procedure

AFM Probes

The surface analysis center houses a state-of-the-art Surface Enhanced Raman Spectroscopy (SERS) instrument. The lab has a Yvon Jobin LabRam ARAMIS, which is available for use by students and post-docs after training. Both solid and liquid samples can be characterized. Glass slides are provided to hold the solid samples. The liquid samples such as molecules, functionalized nanoparticles that are suspended in a buffer solution, can be stored in a test tube or a pipet. The instrument is also capable of x, y and z mapping along with depth profiling.

Technqiue

    RamanSpectroscopy

    Raman spectroscopy is a spectroscopic technique that is used to identify the vibrational, and rotational modes of a material. A monochromatic light, such as a laser, is used to excite the molecules in the material. The monochromatic light interacts with the molecules leading to molecular vibrations, phonons or other excitation that occur through inelastic scattering of photons (also called raman scattering). This interaction results in energy of the laser photons being shifted up or down, giving the vibrational modes of a system. There are several variations of raman spectroscopy and one of them is Surface-enhanced Raman Spectroscopy (SERS).

    SERS is a surface sensitive techniques, where by the raman scattering of molecules on the metal surface is enhanced due to the excitation of localized surface plasmons (electromagnetic theory) or formation of charge-transfer complexes (chemical theory). The enhancement factor can be as much as 10E10 to 10E11, meaning that this technique can detect traces or individual molecules dispersed on metal surfaces.

Instrument

Capabilities

  • Highly automated confocal Raman microscope
  • Sub-micron spatial resolution
  • 4 gratings (600, 1200, 1800, 2400 gr/mm)
  • 2 lasers (532 nm, 633 nm)
  • x10, x50, x100 objectives
  • 4-notch filter selector
  • Two and three dimensional mapping
  • XYZ automated stage
  • Duoscan and Swift options installed

Becoming a user of the Raman

1. Schedule training

  • Basic Training: Standard operation and calibration of the microscope is covered in detail. Users are strongly encouraged to bring their samples to the training session. The training usually takes 2 hours.
  • Advanced Training: Mapping capabilities are covered in detail. At least 5 hours must be logged on the instrument before advanced training may be taken.

2. Complete the following forms and return to SAC

3. Register on the NanoCenter website – once trained you will be able to sign-up for time

Signup calendar
Click on register to create login

Rules for using the Raman instrument

1. Only authorized users (users after training) are permitted to use the instrument.
2. Users of the instrument are expected to keep the instrument neat and tidy.
3. Users are NOT permitted to disconnect connections or remove parts. If the user needs to make changes to the standard instrument setup, they need to contact Dr. Karen Gaskell.
4. Users are required to make a reservation if they need to use the instrument. Users are NOT permitted to use the instrument without a reservation.
5. Users are not permitted to use the instrument beyond the reserved time without extending their reservations, provided there is no one else reserved.
6. If you have made a reservation to use the instrument and if another user is occupying the instrument, you have the right to ask them to leave.
7. If you have any questions or concerns regarding these rules, please see Dr. Karen Gaskell.

Contact

Dr. Karen Gaskell
Department of Chemistry & Biochemistry
University of Maryland, College Park, MD 20742
Phone 301.405.4999 Fax 301.314.9121

Useful Links

Standard Operating Procedure

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