ID-11-P-3150 Microscopy under pressure: Optical micro-spectroscopy technique to study nanomaterials under high hydrostatic pressure

Changes of external conditions, like electric field or pressure, provide additional information on a studied material, for example semiconductor nanoparticles in colloidal suspensions. Under increased hydrostatic pressure of the order of GPa changes of crystalline lattice parameters, reconstruction of surface states and even structural transitions take place which substantially modify optical properties of the studied material. Here we present a special microscope configuration which enables us to study luminescence spectra and kinetics of nanoparticles under pressure up to or even above 20 GPa. The pressure is generated by lever acting on a diamond anvil cell (Fig. 1). The diamond cullet diameter is 0.4 mm and the sample volume is only 0.01 l. Illumination and imaging takes place trough one of the diamonds. The signal is detected by a special micro-spectroscopy apparatus with parallel detection branches for visible (500-1000 nm) and near-infrared (1000-1600 nm) region and detection by 2D focal-plane arrays (based on Si and InGaAs, respectively) or photomultipliers (for time resolved detection). Pressure is monitored using the shift of red luminescence lines from ruby microparticles mixed with a sample. Application of this setup is demonstrated with silicon based nanoparticles whose investigation shed light on the role of surface passivation or embedding matrix on the energies and the direct/indirect character of optical transitions [1,2].

References
[1] K. Kůsová et al.: Luminescence of free-standing versus matrix-embedded oxide-passivated silicon nanocrystals: The role of matrix-induced strain, Appl. Phys. Lett. 101 (2012) 143101.
[2] K. Kůsová et al.: Direct bandgap silicon: Tensile-strained silicon nanocrystals, Adv. Mater. Interfaces 1(2) (2014) in print, DOI: 10.1002/admi.201300042.