P. Basa

Thermopile antennas for detection of millimeter waves

A thermopile structure is proposed for the detection of microwave/millimeter wave radiation. The thermopairs in the suggested linear arrangement function as antennas. 5.58 V/W responsivity was achieved at 100 GHz with 40 serial connected thermopairs. The experimentally observed polarity and frequency dependence convincingly verify the proper detector operation.

Nanocrystal characterization by ellipsometry in porous silicon using model dielectric function

Porous silicon layers were prepared by electrochemical etching of p-type single-crystal Si (c-Si) of varying dopant concentration resulting in gradually changing morphology and nanocrystal (wall) sizes in the range of 2–25nm. We used the model dielectric function (MDF) of Adachi to characterize these porous silicon thin films of systematically changing nanocrystal size. In the optical model both the surface and interface roughnesses have to be taken into account, and the E0, E1, and E2 critical point (CP) features are all described by a combination of several lineshapes (two-dimensional CP, excitonic, damped harmonic oscillator). This results in using numerous parameters, so the number of fitted parameters were reduced by parameter coupling and neglecting insensitive parameters. Because of the large number of fitted parameters, cross correlations have to be investigated thoroughly. The broadening parameters of the interband transitions in the measured photon energy range correlate with the long-range orde...

Nanocrystal Non-Volatile Memory Devices

The physical background and present status of the application of metal-insulator-silicon structures with semiconductor nanocrystals embedded in the insulator layer for memory purposes is breafly summarized.

Introducing nanoscaled surface morphology and percolation barrier network into mesoporous silica coatings

Mesoporous silica thin films were patterned at the sub-micron scale utilizing the ion hammering effect in order to combine the advantages of mesoporous character and surface morphology, while preserving the interconnected pore system or creating laterally separated porous volumes surrounded by nonpermeable compact zones. Porous silica coatings were prepared by a sol–gel method with an ordered and disordered pore system using micellar templates. A hexagonally ordered Langmuir–Blodgett type monolayer of silica spheres was applied as a mask against Xe+ ion irradiation. The ion energy was chosen according to Monte-Carlo simulations to achieve structures with high lateral contrast between irradiated and unirradiated, i.e., masked areas. The disordered pore system proved to be more resistant against ion bombardment. Although the created surface morphologies were similar, the main character of the pore system could be tailored to be interconnected or separated by controlling the ion fluence. Confocal fluorescence images and ellipsometric porosimetry measurements confirmed that the contribution of transition zone between the intact masked and damaged regions to the porosity is negligible. Furthermore, the majority of the porous volume can be preserved as an interconnected pore system by the application of low ion fluence. By increasing the fluence value, however, separated porous volumes can be created at the expense of the total pore volume.

Si 3 N 4 based non-volatile memory structures with embedded Si and Ge nanocrystals

Memory structures with an embedded sheet of separated Si nanocrystals were prepared by low pressure chemical vapour deposition using a Si3N4 control and SiO2 tunnel layers. It was obtained that a properly located layer of Si or Ge nanocrystals can improve both the charging and rettntion behaviour of the MNOS structures simultaneously. Memory window width of about 6.6 V and retention time of 41 years has been achieved for charging pulses of ±15 V, 10 m.s.

New trends in non-volatile semiconductor memories

The construction and the physical background of operation of floating gate, nanocrystal, silicon nitride-based, phase-change, ferroelectric and magnetoresistive memories are breafly summarized.

Si 3 N 4 based non-volatile memory structures with embedded Si nanocrystals

Memory structures with an embedded sheet of separated Si nanocrystals were prepared by low pressure chemical vapour deposition using a Si₃N₄ control layer and SiO₂ or Si₃N₄ tunnel layers. It was obtained that a properly located layer of Si nanocrystals improves the charging behaviour of the MNOS structures. Memory window width of about 6.6 V and retention time of 41 years has been achieved for charging pulses of plusmn15 V, 10 ms.

Electrical and Memory Properties of Non-volatile Memory Structures with Embedded Si Nanocrystals

Memory structures with an embedded sheet of separated Si nanocrystals were prepared by low pressure chemical vapour deposition using a Si₃N₄ control layer and a SiO₂ or a Si₃N₄ tunnel layer. It was obtained that the charging behaviour of structures with SiO₂ tunnel layer was better than with Si₃N₄ tunnel layer

Spectroscopic ellipsometric study of LPCVD-deposited Si nanocrystals in SiNx and Si3N4

Low-pressure chemical vapour deposited and annealed SiN_x/nc-Si/SiN_x and Si₃N₄/nc-Si/Si₃N₄ layers prepared on Si substrates were characterized by spectroscopic ellipsometry. The effective medium approximation model was used to obtain the thickness, the composition and homogeneity of the layers. It was obtained that the deposited nc-Si layer thickness depended on the stoichiometry of the underlying silicon nitride layer

Ellipsometric study of SiN/sub x//nc-Si/SiN/sub x/ multilayers

Low pressure chemical vapour deposited and annealed SiNx/nc-Si/SiNx layers prepared on Si substrates were characterized by spectroscopic ellipsometry. The effective medium approximation model was used to obtain the thickness, the composition and homogeneity of the layers. A significant effect of the deposition time and annealing process was obtained