Equipment available in our labs

In our deposition cluster, users can grow single- or multi-layered thin film samples with different techniques. The cluster allows transferring the samples from one of its chambers to another keeping them under UHV pressure. It consists of:

• A Pulsed Laser Deposition (PLD) system, mostly used to grow oxides and manganites. PLD growth can be monitored by means of Reflection High-Energy Electron Diffraction (RHEED).
• A Chemical Vapor Deposition (CVD) chamber to grow organic layers.
• A metal evaporation chamber to grow metallic (Co, Al, Au, etc.) layers.
• A mask exchange chamber, where masks can be applied over substrates to change the geometry of the layers.
• A load-lock chamber to get sample in and out the cluster.
• A central transfer chamber with a rotating, elongating arm. It serves also as storage unit.

Quantum Design PPMS allows performing several types of experiments in a controlled set of external conditions. A liquid helium based cryostat allows ranging the temperature from 2 to 350 K. Superconducting magnets produce a vertical magnetic field varying from -9 to +9 Tesla. PPMS is mainly used to perform:

• Transport measurements: resistivity vs. temperature/magnetic field curves at constant current can be acquired to determine the transport properties of samples.
• Vibrating Sample Magnetometry (VSM): hysteretic magnetisation vs. external magnetic field curves can be obtained at different temperatures.

Experiments can be done both with field parallel or perpendicular to the sample plane. A Keithley generator can be coupled to the PPMS to increase the range of the applied current or bias voltage. An impedance vs. frequency station to measure samples’ response up to 1 MHz is presently under development.

The Rigaku SmartLab System is a high-resolution four-circle X-ray diffractometer. The system is equipped with a 9 kW rotating Cu-Kα1 anode and the incident parallel beam optics consist of a reflecting mirror and a two-bounce Ge (220) monochromator (Δλ/λ = 3.8x10⁴). Additionally, the system is equipped with an in-plane scattering arm for grazing incidence in-plane surface diffraction measurements.

A customized He-cooled sample cell with a Beryllium dome can be used to perform X-ray diffraction and reflectivity measurements at low temperatures down to 10 K. The XRD system is mainly used to perform:

• X-ray reflectivity measurements of thin monolayers or multilayers in order to extract film thicknesses and interface roughnesses;
• Out-of-plane (00L) X-ray diffraction measurements in order to determine out-of-plane lattice parameters of thin film samples;
• Reciprocal space maps in order to study strain effects in thin film heterostructures.

Our laboratory is equipped with an NT-MDT NTEGRA AFM microscope. We use this microscope to characterize the roughness of our samples, on a typical lateral scale of microns. The vertical resolution of the instrument is under the nanometer scale. The instrument works in ambient conditions. Both contact and non-contact mode scanning can be performed. Topographic and phase images can be simultaneously acquired. Optionally, magnetic tips can be used to study magnetic properties at room temperature.

Covering the far-infrared (40-700 cm^-1) and mid-infrared (400-4000 cm^-1) ranges, the "Elli" is the workhorse of our ellipsometry lab. It is based on Bruker IFS 113 Fourier-transform infrared spectrometer with external He cooled bolometer as the detector. For the mid- and far- infrared ranges we use different sets of beam-splitters, polarizers and retarders. CryoVac cryostat provides temperature range of 10-350 K.

The ellipsometry chambers, attached externally to the spectrometer, are evacuated to avoid absorption of the IR light in atmosphere. The angle of incidence can be changed manually in discrete 2.5 deg steps in the range of 65 to 90 deg by repositioning the detection-branch mirrors in the chamber.

The ellipsometer is working in polarizer, optional retarder, sample, rotating analyser mode. The optional retarder is based on internal reflection in ZnSe (mid-infra) or Si (far-infra) prism - otherwise gold coated mirror is flipped into the reflection point. We have recently implemented ZnSe rotating compensator for the mid-infrared range.

Options:

• In-situ photo doping of the sample through side window in the cryostat and chamber.
• In-situ sample rotation for anisotropic materials.
• High-temperature stage for temperatures above 350 K, we can safely reach 700 K.

For visible, nir and uv, we use commercial ellipsometer from Woollam.

We have built an ellipsometer operating in the THz range (3-85 cm^-1 or 0.1-2.5 THz). It is based on time-domain spectroscopy - we use femtosecond laser from Menlo Systems producing 100 fs pulses of 780 nm light, with total output about 100 mW that powers the area emitter antenna (GigaOptics TeraSED) and dipole antenna detector (Menlo Systems). The polarizers are tandems of free standing wire-grids (Specac) and the ellipsometer operates in rotating analyzer mode. Our system features alignment-free variable angle of incidence in the range 45-90 deg, where 90 deg is straight-through/transmission configuration. The system is equipped with He-flow cryostat for temperature range 10-350 K from CryoVac.

Infrared response of small, irregular samples can be mesured by robust normal incidence reflectivity technique with in-situ gold coating. The spectrometer is based on the Michelson-type interferometer and covers the range from 5 to 10000 cm^-1(provided with FIR and MIR sources). The sample compartment was reorganized with elliptical and flat mirrors to form the beam path to the sample placed in the cryostat for temperature dependent measurements. The experimental setup consists of 3 major parts:

• Fast-Fourier transform spectrometer (Bruker 70v).
• reflection unit with a low temperature cryostat.
• external detector – helium cooled bolometer.

The TellMag is our next project. We have most of the parts and are presently building it.