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The present work reports the evolution and growth of GeGaAs(O) polytype nanoislands over GaAs p‐type substrate with photoemission application in mind. Several morphological transformations from NIs to simultaneously present nanopits/holes are observed as a function of annealing parameters that is, temperature (350‐800°C) and time (5‐90 minutes). Structural and elemental analyses are executed using atomic force microscopy, scanning electron microscopy and energy dispersive X‐ray spectroscopy. Photoemission current of the nanostructured surfaces, measured upon exposure from 265 nm light emitting diode, is found to depend on the nanoislands size, which in turn depends on the annealing parameters. A maximum photoelectric emission is obtained for structure annealed at 650°C for 60 minutes, upon which an increment of roughly two orders of magnitude is observed.

This study incorporates the structural and magnetic characterization of epitaxial Ni80Fe20 films grown by direct current magnetron sputtering on MgO(001) and MgO(001)||VN(001) substrates. A series of samples grown with different N2 flow settings for the deposition of VN and similar permalloy deposition parameters was utilized to investigate the effect of morphological evolution and buffer layer induced strain on the magnetic properties of Ni80Fe20. X-ray diffraction analysis reveals an epitaxial nature of the VN(001) and Py(001) films grown on MgO substrates. Angular dependent magneto-optical Kerr effect characterization reveals a cubic anisotropy for Ni80Fe20 on MgO with a coercivity of ∼0.8 Gauss along the easy directions. Incorporating an epitaxial VN buffer, the structures showed a transition from a cubic to isotropic magneto-crystalline anisotropy with coercivity varying from 2.5 to 25 Gauss for Ni80Fe20 deposition on VN (with N2 varying from 5 to 12 sccm). The variation is attributed to the microstructural evolution of the Ni80Fe20 to 3D structures along with an induced structural strain., This work was supported by funding from the Icelandic Research Fund Grant Nos. 218029–051, 228951–051 and 207111–051.

Publisher's version (útgefin grein), Films of SiGe nanocrystals (NCs) in oxide have the advantage of tuning the energy band gap by adjusting SiGe NCs composition and size. In this study, SiGe-SiO2 amorphous films were deposited by magnetron sputtering on Si substrate followed by rapid thermal annealing at 700, 800 and 1000 °C. We investigated films with Si:Ge:SiO2 compositions of 25:25:50 vol.% and 5:45:50 vol.%. TEM investigations reveal the major changes in films morphology (SiGe NCs with different sizes and densities) produced by Si:Ge ratio and annealing temperature. XPS also show that the film depth profile of SiGe content is dependent on the annealing temperature. These changes strongly influence electrical and photoconduction properties. Depending on annealing temperature and Si:Ge ratio, photocurrents can be 103 times higher than dark currents. The photocurrent cutoff wavelength obtained on samples with 25:25 vol% SiGe ratio decreases with annealing temperature increase from 1260 nm in SWIR for 700 °C annealed films to 1210 nm for those at 1000 °C. By increasing Ge content in SiGe (5:45 vol%) the cutoff wavelength significantly shifts to 1345 nm (800 °C annealing). By performing measurements at 100 K, the cutoff wavelength extends in SWIR to 1630 nm having high photoresponsivity of 9.35 AW−1., This work was supported by TE Contract no.30/2018 (PN-III-P1-1.1-TE-2016-2050, within PNCDI III), M-ERA.NET PhotoNanoP Contract No. 33/2016, PCE Contract No. 122/2017, PCCDI Contract No. 75/2018, and financed by CNCS-UEFISCDI, and by Romanian Ministry of Research and Innovation through NIMP Core Program PN19-03 (Contract No. 21N/08.02.2019)., "Peer Reviewed"

We investigate the photoluminescence properties of structures comprising of Si1-xGex nanoparticles (NPs) within SiO2, GeO2, TiO2 and Ta2O5 oxide matrices. Of the investigated structures, it was observed that the structures with GeO2 and TiO2 matrices provide increased spectral response (at ~907 and 844 nm respectively) and increased PL intensity. The improved PL characteristic have been attributed to increased diffusion barrier against oxygen which otherwise would result in formation of unwanted oxide at the film-oxide interface, thereby deteriorating the optical properties., This work is partially funded by the Icelandic Research Fund Grants nos. 218029 and 196141., Pre-print (óritrýnt handrit)

Publisher's version (útgefin grein), Multilayer structures comprising of SiO2/SiGe/SiO2 and containing SiGe nanoparticles were obtained by depositing SiO2 layers using reactive direct current magnetron sputtering (dcMS), whereas, Si and Ge were co-sputtered using dcMS and high-power impulse magnetron sputtering (HiPIMS). The as-grown structures subsequently underwent rapid thermal annealing (550-900 degrees C for 1 min) in N-2 ambient atmosphere. The structures were investigated using X-ray diffraction, high-resolution transmission electron microscopy together with spectral photocurrent measurements, to explore structural changes and corresponding properties. It is observed that the employment of HiPIMS facilitates the formation of SiGe nanoparticles (2.1 +/- 0.8 nm) in the as-grown structure, and that presence of such nanoparticles acts as a seed for heterogeneous nucleation, which upon annealing results in the periodically arranged columnar self-assembly of SiGe core-shell nanocrystals. An increase in photocurrent intensity by more than an order of magnitude was achieved by annealing. Furthermore, a detailed discussion is provided on strain development within the structures, the consequential interface characteristics and its effect on the photocurrent spectra., M-ERA. NET project PhotoNanoP UEFISCDI Contract no. 33/2016, PCE project UEFISCDI Contract no. 122/2017 and by Romanian Ministry of Research and Innovation through NIMP Core Program PN19-03, contract no. 21 N/08.02.2019 and by the Technology Development Fund of the Icelandic Centre for Research, grant no. 159006-0611., "Peer Reviewed"

The study presents the dynamics of solid-state dewetting of silver (Ag)-film annealed in N2 ambient, analyzed by atomic force microscopy and scanning electron microscopy. Varying the annealing parameters (i.e. temperature and time) and Ag-film thicknesses were taken into account, to determine their effect over the solid-state dewetting of Ag-films. Several morphological evolutions from nanohole to the presence of metastable nanorings were observed. It was determined that structures annealed at high temperature (≥900 °C) and/or time (≥2 h) results in formation of metastable nanorings and whose geometrical aspects and population grew with increasing film thickness. Possible applications of the structures for fabrication of silicon nanowire arrays and photo-emitters are briefly described.