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Tandetron Laboratory – Infrastructure

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3 MV Tandetron Particle Accelerator

The 3 MV tandetron particle accelerator was installed and commissioned in 2017 and has two multicusp sources for H and He -ions with current thresholds of ~ 1mA before the low energy magnet, and ~ 200 µA post-acceleration. A Heavy Ion (HI) Sputtering Source is also included in the accelerator infrastructure. The availability of a HI Sputter Source has created many possibilities for research on Ion-Solid Interaction research. In the basic ion-solid interaction research domain, measurements of fundament parameters (Stopping force S(E), straggling, effective ranges for analysis), which are involved in the physics of slowing down processes of HI in heavy metals will be carried out. Furthermore, this provides appropriate infrastructure to users to perform surface characterization elemental depth profiling with highly charged heavy ions particularly in the fields of nano-sciences, materials engineering, condensed matter and characterization of samples used in nuclear physics experiments at the Separated Sector Cyclotron (SSC).

Particles acceleration:

  • Accelerator terminal voltage tunable from 80 kV to 3 MV (source injection voltage is up to 30 kV).
  • H+, He+ and He++ beams in standard configuration with maximum energies of 3.4, 3.4 and 5.1 MeV, respectively.
  • Beam spot size from 1 mm to 6 mm for solid state beamline and up to ~1µm for the Nuclear Microprobe (NMP) beamline.
  • Maximum beam current of ~100 µA on target depending on ion species and energies.
  • 3He, 15N and 16O beams are also available for nuclear reaction analysis (NRA) or elastic recoil detection analysis (ERDA).

Ion Beam Analysis Techniques

Rutherford Backscattering Spectrometry (RBS)

RBS is based on Rutherford’s experiment which lead to the discovery of the nucleus of the atom. Today RBS, is a powerful tool for determining elemental information, for example in the characterization of thin films. Helium ions (alpha particles) are accelerated to energies between 1 and 4 MeV. These alpha particles are then focused on the sample to be analysed. Measurements are done in a vacuum chamber where an area of a few square millimetres is analysed. A silicon detector tilted at 165° detects the backscattered alphas from the sample. RBS analysis is used mostly for determining the composition and the depth distribution of elements but by aligning the crystallographic axes of the sample to the incoming alpha particles, RBS channelling analysis provides information about the crystal structure of the sample. RBS is a non-destructive and multi-elemental analysis technique.

Elastic Recoil Detection Analysis (ERDA)

The quantitative and sensitive analysis of light elements in thin films is in general a non-trivial task in materials science, since there are only a few techniques available to get reliable and accurate profiles. Elastic recoil detection (ERD) using energetic heavy ions is such a technique. Recoiled ions scattered off a thin film by an energetic heavy ion beam impinging the surface at a glancing angle are detected under forward direction and analysed for their nuclear charge or mass and energy. A sensitivity in the ppm region with a depth resolution of some 10 nm and a depth range of 1 micron is obtained in standard ERD set-ups.

Nuclear microprobe (microPIXE)

Since its installation the nuclear microprobe (NMP) has been successfully used in the analysis of samples from fields including archaeology, biology, geology, materials science and medicine. The microprobe target chamber is a modified version that replaced the conventional Oxford Microbeams chamber delivered in 1991. A custom-made lid has been installed that allows for stepper motor control of the target ladder in the X-, Y- and Z-directions. Charged particles (protons, alpha particles or heavy ions) are used to create inner-shell vacancies in the atoms of the specimen. Protons of 1-4 MeV energy are most often used. Their slowing down in matter is smooth and well characterized, with little scattering and deflection. The process is therefore easy to quantify. PIXE spectra are usually collected in energy-dispersive mode and all elements with atomic numbers above 10 (Na and above) can in principle be detected at once. The characteristic X-rays of lighter elements are absorbed in the windows of routinely used Si(Li) or HPGe detectors. Typically reported sensitivities are 10-20 ppm for Na to Cl and 1-10 ppm for Ca and heavier elements. No information related to chemical identity, coordination chemistry or oxidation state of a particular element could be directly obtained. The GeoPIXE software package is used for off-line PIXE data analysis and quantitative imaging. For point PIXE analysis GUPIX software can also be used.

Physical Properties Measurement System (PPMS)

This system allows for the measurement of electrical (electrical conductivity, Hall effect, etc), thermal (thermal conductivity thermo-power, specific heat, etc.), and magnetic (DC magnetization and AC susceptibility) properties at magnetic fields up to an optional 7, 9 or 16T (superconducting solenoid magnets), and accurately controlled temperatures in the range 1.9 < T < 400K. Temperatures up to 1000K can be obtained with an optional “oven” insert. The apparatus is PC controlled and is completely programmable (such that a prolonged sequence of measurements under varying temperature and field values or sweeps can be done). The PPMS is readily expandable, with a variety of specialist specimen stages and measurement options and very user friendly. It is supplied either in a conventional cryostat dewar, which is very economical in the use of liquid helium, or in a cryostat with built-in cryo-refrigerator (EverCool option).

Atomic Force Microscope (AFM)

A high resolution AFM imaging system which consists a DI Nanoscope V SPM control station, a Dimension V Scan head with a hybrid XYZ closed loop scanner, a motorized stage with a sample chuck size of 150 mm in diameter, and an optical microscope which provides real-time color video display at a 1.5 µm resolution with a maximum field of view of 675 µm. Includes an integrated vacuum system which can be activated to lock large samples on the sample stage. Samples can be scanned to a maximum scan-field of 105 µm2. The Nano-Man V AFM equipped with a VT-103-3K-2 acoustic enclosure, is a lithography dedicated system capable of both nano-lithography and nano-manipulation in a humidity controlled ambient in virtually all three basic AFM imaging techniques, viz Tapping Mode, Contact Mode, and Non-Contact Mode. Additional supported imaging techniques include Magnetic Force Microscopy (MFM), Electric Force Microscopy (EFM) and Force Imaging through Force distance curves. The Nanoman AFM also has capabilities to function as an STM. With such a wide variety of imaging techniques this make the Nanoman V AFM a most valuable a surface analytical tool for nano-characterization of a wide range of materials. Surface features such as grain sizes, step-heights and the overall surface roughness can be quantified at near atomic resolution. The special lithographic capability of Nanoman V AFM makes it an even more valuable tool in the low-dimensional semiconductor device fabrication technology.

X-ray Diffraction (XRD)

The XRD facility offers a first class service in terms of technical and/or scientific assistance samples, a high throughput of samples with excellent data quality. The XRD lab welcomes all academic institutions on a regional, national and continental level. The facility comprises of a BRUKER X-ray diffractometer for microstructural characterization of specimens using a non-destructive technique. Information obtained from the diffractogram benefits a wide range of Departments such as Chemistry, Polymers, Physics, Geology, Engineering, Electronics, Pharmaceutics, thus covering a broad field of research comprising nanomaterials, fuel cells, catalysts, bio-coatings, residual stress in surface coatings, stress determination in laser bent steel plates for automotive industry, soils study in wine farms production.

Multi-Functional Integrated Optical Characterization Platform

For thin film Optical Analysis, we are able to do the following:

  1. Absorption, transmission, and reflectivity in the wavelength range from 200 to 2600 nm
  2. Measurement of diffuse reflection, including specular reflection using an Integrating Sphere from 200 to 2600 nm.
  3. Reflectometry technique for transparent film thickness measurement by measuring reflectance for different wavelengths
  4. Ellipsometry to determine the optical constants, refractive index, surface roughness and film thickness.
  5. Fluorescence.
  6. Raman operating at 532 nm which is good for powdered samples with low fluorescence and materials where C-OH structural information is important.