We have been utilizing the techniques listed in this page for analyzing defects, extremely low concentration of impurities in ultra-high purity materials for microelectronics, and nanoscale features and heterostructures to allow the development of new devices, such as solar cells, quantum dot arrays, nanosensors... Aside from the conventional analytical techniques, nanoprobes specialized in the characterization of semiconductor nanomaterials and devices received much of our attention, as they allow measuring a set of time resolved or energy resolved properties at nanoscale. Of particular importance are a set of Near field Optical Scanning Microscopy (NSOM) based scanning and spectroscopic techniques. We have modified NSOM to explore the dynamics of carriers, or effect of local strain on the electronic properties in low dimension semiconductor materials, or piezolectricity in PVDF or NKBT,... Lifetime is measured in NSOM based pump-probe system. We could analyze charge carrier recombination processes along with local strains at the sub-micron and deca-nanometer scales. The new added functionalities to NSOM are extremely important for deciphering, for instance, the complex growth of nanomaterials, mechanisms of defect nucleation and growth, the physics underlying multi-photon absorption mechanism, the generation of charge carriers and the recombination and trapping of carriers, the involvement of particles and quasi-particles during optical and electronic transitions. Besides, we have nicely combined several among the known contact nanoprobe modes to get correlated data on single nanofeatures found in the materials we have grown.

If you are interested in collaboration on nanomaterial and device characterization using the listed techniques, This email address is being protected from spambots. You need JavaScript enabled to view it.This email address is being protected from spambots. You need JavaScript enabled to view it.

 

Fabrication of Nanomaterials

  • Rapid Thermal Chemical Vapor Deposition (RT-CVD) for growing SiGe quantum dots
  • Atomic Layer Deposition (ALD) for making ultra-sharp heterostructure, and for making quantum dots
  • Pulsed Laser Deposition (PLD), and
  • Ion Implantation: material modification (N, S, Se hyperdoping), self-implantation for imputirty gettering, radiation ressitance tests (Proton)

Microelectronic, MEMS, and Solar Cell Processing

  • RT-CVD, LP-CVD, PECVD, Epitaxy, CMOS processes, Evaporation, Reactive Ion Etching (RIE), Sputtering, Focused Ion Beam (FIB)
  • Ion Implantation for heavily doping trenches
  • Photolithography, E-Beam lithography (EBL), Heidelberg Mask Writer, Mask aligner, Mask Design
  • Thermal Diffusion in open tube furnaces, CMP, Wafer bonding
  • Screen printing. I contributed to the development of Integral screen printing at IMEC (KUL, Belgium). This technology is used by all siliocn photovoltaic industry.
  • Micro-spray and Inkjet, Airless Spray, Spin-on, and
  • Electrochemistry methods, used for electro-deposition of thin film CdS as well as for making porous silicon and porous alumina.

Characterization of Optoelectronic Devices (photovoltaic cells and optical sensors)

  • I-V with standard sun simulator, solar cell basic characteristics, delineation of conduction modes, ...
  • Internal/External Quantum Efficiency IQE(λ) / EQE(λ): P-N junction model, device geometry parameters, charge carrier parameters
  • Capacitance Spectroscopy C-V: junction type, doping concentration,...
  • Laser Beam Induced Current (LBIC): surface recombination velocity, minority carrier dynamics, carrier depth profiling through wavelength dependent LBIC ...
  • Electron Beam Induced Current in Scanning Electron Microscopy (EBIC/SEM): similar to LBIC, generation, recombination velocity by single defect grain boundary, horizontal and vertical dislocations
  • Surface Photovoltage (SPV), carrier dynamics at the surface, minority carrier diffusion length.

Optical Characterization of Materials (e.g., photovoltaic materials)

  • UV-Vis-NIR Spectroscopic Ellipsometry, effective medium models, n(λ), k(λ), thickness of ultra-thin layers, identification of material phases, etc.
  • Optical Absorption,
  • Reflectance (Specular), and
  • Diffuse Reflectance, using Integrating Sphere & Spectrometer; used for developing textured surfaces on polycrystalline silicon,

Nanoprobe Techniques for Nanomaterials Characterization

  • Confocal Scanning Laser Microscopy (CSLM),
  • Near field Scanning Microscopy (NSOM)
  • Modified version of NSOM to measure carrier recombination lifetime, diffusion length, and local strains.
  • Confocal Fluorescence microscopy,
  • Confocal Raman microscopy for depth profiling and imaging impurities and/or stresses (200 nm resolution),...,
  • Tip Enhanced Raman Spectroscopy (TERS) for imaging materials composition (within single nanofeature), bond sates,...
  • Atomic Force Microscopy (AFM),
  • Scanning Kelvin Probe (SKP); measures voltage gradient, space-resolved conductivity,
  • Spreading Resistance imaging; for detecting doping type and concentration,
  • Scanning Capacitance imaging, and
  • Scanning Tunneling Microscopy (STM).

        These techniques are used in standalone or coupled to obtained correlated data and unique set of materials properties.

        In-situ AFM is used to decouple the topography effects from the material response.

Charge Carrier Dynamics

  • Recombination lifetime: Microwave Photoconductance Decay (μPCD) for Recombination lifetime mapping and profiling, SPV, for minority carriers
  • Generation lifetime: C-V of CMOS devices, C-t, andZerbst Analysis,
  • Minority carriers Diffusion Length: High resoultion Light Beam Induced Current (LBIC),  EBIC/SEM,
  • Cathodoluminescence (CL/SEM), and
  • Pump-probe Time-resolved NSOM (τ-NSOM) for lifetime mapping.

Spectroscopy Techniques

  • Deep Level Transient Spectroscopy (DLTS),
  • Photo-Induced Current Transient Spectroscopy (PICTS),
  • Injection Level Spectroscopy by μPCD,
  • Cryogenic Photoluminescence (PL), and RT Scanning PL
  • Raman scattering spectroscopy, confocal Raman, and TERS,
  • Spectroscopic Ellipsometry,
  • Synchrotron FTIR, and
  • Synchrotron X-ray Photo Emission Electron Microscopy (XPEEM).

Material Structural Analysis

  • X-ray diffraction (XRD), Synchrotron XRD Submicron Mapping (x-ray probe) of multi-crystalline materials,
  • X-Ray Topography (XRT), Cross-section XRT, Limited Projection XRT (LP-XRT),
  • Delineation of Crystal defects using chemical etching (Sirtl, Secco, and Wright etch) and microscopy,
  • Conventional TEM, Atomic resolution STEM, Z-contrast, and EELS,
  • High resolution Field Emission-SEM (FE-SEM) with Energy-dispersive X-ray spectroscopy (EDX),
  • In-situ material modification in environmental TEM, and
  • TEM sample preparation using conventional and Focused Ion Beam with SEM (FIB-SEM) techniques.

Measurement of Impurity Concentration In High Purity Materials

  • Standard Secondary Ion Mass Spectroscopy (SIMS),
  • Special high resolution SIMS for lateral and depth imaging of impurities in high purity semiconductors, and
  • Extremely low concentration (1010 cm-3 ) electrically active impurities using DLTS.

Materials Mechanical Properties

  • WiTec piezoresponse force microscopy(PFM) for scanning electro-mechanical properties of piezoelectric and ferroelctric nanomaterials
  • Tensile test of nanomaterials
  • Nanoindentation and Nanoscale scratching (Hysitron),
  • Disc bending, and Three-point bending.