In order to obtain atomic-flat and furthermore single-terminated substrates, we treat the commercial single crystal substrates with a set of chemical etching and annealing process in our high temperature furnace or reflow oven.
Our PANalytical Empyrean X-ray diffractometer includes high-resolution optics (monochromator, mirrors, slits, analyzer crystal, etc.), 4-axis sample cradle, and 2D detector, which allows the ultra-fast measurements of rocking curves, reciprocal space mapping, X-ray reflectivity in minutes!
Our cryogen-free PPMS from quantum design serves as the most powerful probe to characterize the electrical and magnetic properties of our thin films. Advanced options (ADR, ETO, VSM, AC susceptibility, Sample Rotator) are available.
FACILITIES
Surface Preparation Facility
In-situ Probes-RHEED, XPS and Auger Spectroscopies
Atomic Force Microscope
Laser MBEs
Laser MBEs
High Resolution X-ray Difractometer
9 Tesla Physical Properties Measurement System
We check the surface roughness of each thin film by performing atomic force microscopy. The scans are performed in both 'Contact mode' and 'Non-contact mode'. One can also capture the magnetic domains with this AFM machine using a magnetic tip. The associated software equipped AFM can calculate both line and area roughness during the scan. All measurements are performed at the room temperature and at ambient condition.
ARPES and HREELS coming in 2018...
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Three state-of-the Laser Molecular Beam Epitaxy (L-MBE1, 2 and 3) machines have been developed in the Chakhalian's Laboratory for Artificial Quantum Materials with the following unique capabilities:
(i) the stoichiometric and non-stoichiometric transfer of a materials composition from target to substrate,
(ii) practically free choice of background pressure during the fabrication using reactive process gases (e.g. all the systems can be operated with O2, ozone, CO2, N2 and Ar).
(iii) highly non-equilibrium growth capable of kinetically stabilized metastable phases of materials unattainable via conventional 'slow' bulk synthesis or traditional all-oxide MBE. In addition, Chakhalian's group has access to a conventional 4-cell all-oxide MBE to complement the LMBE growth effort.
During synthesis, the LMBE uses a high power UV pulsed laser beam (λ = 248 nm for KrF mixture, up to 800 mJ/pulse, 20 ns duration and up to 50 Hz pulse-rate) in order to ablate material from a target and transfer the ionized species to a substrate in the highly non-equilibrium way. The structural quality is monitored in-situ unique high pressure RHEED capable of operating in 400 mTorr O2 pressure (STAIB Instr.)
To ensure the availability of the layer-by-layer (LBL) growth and the perfect stoichiometric quality of resulting quantum structures Chakhalian's group maintain precise control over the structural quality on the sub-unit cell scale with a ultra high-speed 2D-RHEED imaging system. Proper chemical composition of the films is crucial for the quality of materials. To ensure desired stoichiometry during the growth we developed an innovative in-situ X-ray spectroscopy (XRF) approach operating in high oxygen pressure, which previously was available only as a part of semiconductor thin film growth in ultrahigh vacuum. The high pressure XRF system is capable to collect X-ray spectra generated by electrons of the RHEED system, which ensure that X-ray events originate only from the film surface. One of the key components which have been recently installed into the XRF detector is a specially developed polymer window, which for the first time allows for low Z-elements data collection including oxygen. Furthermore, the L-MBE2 is significantly upgraded to incorporate the advanced in-situ photoelectron spectroscopies such as Auger, EELS and Mg/Al dual-cathode XPS - capable of operating in up to 10-9Torr of base pressure; the innovative design is based on a high collection efficiency double-stage cylindrical analyzer DESA-150 recently developed in collaboration with STAIB Instruments. This implementation is unique. One of the unique features of L-MBE3 is its full Omicron sample holder compatibility which allows to transfer samples between various instruments without exposing their surface to ambient, e.g. ARPES, STM, HREELS etc.
-> Video about Pulsed Laser Deposition
Laser MBEs or Pulsed Laser Deposition