Variable angle spectroscopic ellipsometry (VASE) and ellipsometric porosimetry (EP) have been used to study the effect of treatment with hexamethyldisilazane (HMDS) on the porosity of silica xerogel ...films. Chemical modification of the surface with HMDS was found to reduce the porosity by approximately 15%. This reduction was connected with changes which occur in the silica network, with further condensation or the reaction between neighbouring trimethylsilyl (TMS) surface groups being possible causes.
•Grain size of the Nd doped ZnO layers varies from 50nm to 76nm by SEM.•From Raman, the LO phonon is slightly red-shifted and broadened.•Presence of crystalline defects in the ZnO lattice confirmed ...was by Raman studies.•A red shift was also observed for Nd doping of ZnO thin films confirmed by PL.
Thin films of Zn1−xNdxO were deposited by spray pyrolysis on Si(111) substrates preheated at 400°C temperature and were studied as a function of neodymium (Nd)-doping concentration. X-ray diffraction (XRD) patterns confirmed that the deposited films possess hexagonal wurtzite ZnO structure. Further, it is observed that the doped films show a preferential orientation along the c-axis (002), which is perpendicular to the substrate. The un-doped films seem to be having a bit low-crystallinity, which is corroborated by the scanning electron microscope (SEM) analysis that showed nano-crystalline like features. Further, SEM analysis showed that the Nd doping triggers the formation bubble-like structure on top of the nano-crystalline structure. The SEM microstructures are interpreted with the Micro-Raman studies. Photoluminescence (PL) and XRD characterizations indicate that above 5at.% doping concentrations, the Nd atoms preferentially agglomerate in the large islands.
Direct wafer bonding between high-density-plasma chemical vapour deposited (HDP-CVD) oxide and thermal oxide (TO) has been investigated. HDP-CVD oxides, about 230nm in thickness, were deposited on ...Si(001) control wafers and the wafers of interest that contain a thin strained silicon (sSi) layer on a so-called virtual substrate that is composed of relaxed SiGe (4mum thick) on Si(001) wafers. The surfaces of the as-deposited HDP-CVD oxides on the Si control wafers were smooth with a root-mean-square (RMS) roughness of < 1nm, which is sufficiently smooth for direct wafer bonding. The surfaces of the sSi/SiGe/Si(001) substrates show an RMS roughness of > 2nm. After HDP-CVD oxide deposition on the sSi/SiGe/Si substrates, the RMS roughness of the oxide surfaces was also found to be the same, i.e., > 2nm. To use these wafers for direct bonding the RMS roughness had to be reduced below 1nm, which was carried out using a chemo-mechanical polishing (CMP) step. After bonding the HDP-CVD oxides to thermally oxidized handle wafers, the bonded interfaces were mostly bubble- and void-free for the silicon control and the sSi/SiGe/Si(001) wafers. The bonded wafer pairs were then annealed at higher temperatures up to 800 deg C and the bonded interfaces were still found to be almost bubble- and void-free. Thus, HDP-CVD oxide is quite suitable for direct wafer bonding and layer transfer of ultrathin sSi layers on oxidized Si wafers for the fabrication of novel sSOI substrates.
Silica xerogel films with low dielectric constant were prepared by means of a sol–gel spin-coating method using different aging and hydrophobisation conditions. Non-destructive variable angle ...spectroscopic ellipsometry (VASE) studies allow a complete characterization of the xerogel films, in terms of thickness, optical constants and void fraction. The electronic and ionic contributions to the static dielectric constant of the xerogel films were calculated from the refractive index in the visible range and from infrared transmission spectra, respectively. The origin of the differences between the contributions to the static dielectric constant of the xerogel films produced with different preparation conditions is discussed.
The orientation of the perylene derivatives 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA) and N,N′-dimethyl-3,4,9,10-perylenetetracarboxylic diimide (DiMe-PTCDI) on sulphur passivated ...GaAs(100) surfaces and its impact on the optical properties were studied by means of near-edge X-ray absorption fine structure spectroscopy (NEXAFS), Raman spectroscopy, and variable angle spectroscopic ellipsometry (VASE). NEXAFS shows that PTCDA molecules lie flat on the substrate with their molecular plane parallel to the substrate surface. DiMe-PTCDI molecules grown on the same type of substrates are tilted with respect to the substrate surface and are predominantly oriented with their long axis parallel to the 110 direction. The optical properties of these films investigated by VASE show that the DiMe-PTCDI films exhibit a much stronger optical anisotropy than the PTCDA films.
Fabrication of strained silicon on insulator (sSOI) substrates by wafer bonding and layer splitting is described in this paper. The sSi layer of 20
nm thickness is obtained on an 8
in. virtual ...substrate that consists of a plastically relaxed SiGe layer grown epitaxially on Si(0
0
1) by chemical vapor deposition (CVD). The plastic relaxation of the initially pseudomorphic SiGe layer is mediated by helium implantation into the Si wafer below the SiGe/Si(0
0
1) interface and subsequent annealing. A SiO
2 layer is grown by plasma enhanced (PE) CVD on the sSi/virtual substrate prior to wafer bonding. The PECVD oxide layer is used to compensate the thermal stress existing at the bonding interface during annealing.
The SiO
2/sSi/virtual substrate wafers are then implanted with hydrogen at a high dose (3.5
×
10
16
H
2
+
cm
−2) and subsequently bonded to Si(0
0
1) handle wafers. Subsequent annealing of the bonded wafer pair leads to the transfer of the implanted layer (containing the sSi layer) from the virtual substrate to the Si handle wafer. The final sSOI structure is realized by subsequent chemo-mechanical polishing followed by selective wet chemical etching. The sSOI substrate shows good thickness uniformity (∼20
nm) of the sSi layer over the entire 8
in. area and the strain measurements indicate a value of ∼0.66%.
Spectroscopic ellipsometry was employed to determine the complex refractive index and dielectric function of a
N,
N′-dimethylperylene-3,4,9,10-dicarboximide (DiMe-PTCDI) film grown on S-GaAs(100). ...The optically biaxial film shows strong anisotropy. The maximum difference of the dielectric function is observed in the substrate plane. In the low energy absorption free near infrared range maximum and minimum values for the dielectric tensor components of approximately 4.5 and 2.6 are determined in the film plane while a value of 3.2 is determined for the direction perpendicular to the surface. The strong in plane anisotropy is confirmed by infrared reflection spectroscopy. From the investigations we can conclude that the DiMe-PTCDI molecules in the organic layer are predominantly oriented with their long axis parallel to the 011 direction of the GaAs substrate and tilted with their molecular plane by an average angle of ∼62° with respect to the substrate plane.
The target of our investigation is the evaluation of the effect of decreasing thickness on the relative permittivity of dielectric films for high advanced interconnects of IC’s. Two kinds of ...SiCOH-films with similar chemical composition and thickness between 70 and 830
nm were deposited by spin coating (“SOD”) or PECVD (“CVD”) on silicon wafers. The relative permittivity was determined by CV-measurement and its components of polarization response are deduced from ellipsometric and FTIR measurements.
The target of our investigation is the evaluation of the effect of decreasing thickness on the relative permittivity of dielectric films for high advanced interconnects of IC's. Two kinds of ...SiCOH-films with similar chemical composition and thickness between 70 and 830nm were deposited by spin coating ('SOD') or PECVD ('CVD') on silicon wafers. The relative permittivity was determined by CV-measurement and its components of polarization response are deduced from ellipsometric and FTIR measurements.
We report the results of non-resonant and resonant Raman scattering in orthorhombic nanocrystalline CuInS sub(2) semiconductor, supported by density functional first principle lattice dynamics ...calculations. A larger number of dominant phonon modes in comparison with standard tetragonal CuInS sub(2) phases is shown to be associated with peculiarities of cation sublattice ordering and is the "fingerprint" of the corresponding structural polymorph. Good overall agreement is found between theoretical and experimental phonon mode frequencies.
