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  • 1.
    Abedin, Ahmad
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Noroozi, Mohammad
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Material- och nanofysik, Funktionella material, FNM.
    Primetzhofer, Daniel
    Östling, Mikael
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Radamson, Henry.H
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    GeSnSi CVD Epitaxy using Silane, Germane, Digermane, and Tin tetrachlorideArtikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this study, strain relaxed and compressive strained Ge1-x-ySnxSiy (0.015≤x≤0.15 and 0≤y≤0.15) layers were epitaxially grown on Si substrate in a chemical vapor deposition reactor at atmospheric pressure. Digermane (Ge2H6) and germane (GeH4) were used as Ge precursors and tin tetrachloride (SnCl4) was used as Sn precursor. The growth temperature was kept below 400ᵒC to suppress Sn out diffusion. The layers crystal quality and strain were characterized using XRD, high resolution reciprocal lattice mapping and transmission electron microscopy and the surface morphology was investigated by atomic force microscopy (AFM). Furthermore, the low temperature epitaxial growth up to 15% Si atoms incorporation in Ge0.94Sn0.06 was demonstrated by adding silane (SiH4) as Si precursor. Sn contents calculated from high resolution XRD patterns were confirmed by Rutherford backscattering spectroscopy which shows that Sn atoms are mostly positioned in substitutional sites. AFM analysis showed below 1nm surface roughness for both strained and strain relaxed GeSn layers which make the promising materials for photonics and electronics applications.

  • 2.
    Hamawandi, Bejan
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Material- och nanofysik, Funktionella material, FNM.
    Noroozi, Mohammad
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Material- och nanofysik, Funktionella material, FNM.
    Jayakumar, Ganesh
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Ergül, Adem
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Material- och nanofysik, Funktionella material, FNM.
    Zahmatkesh, Katayoun
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Material- och nanofysik, Funktionella material, FNM.
    Toprak, Muhammet S.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Material- och nanofysik, Funktionella material, FNM.
    Radamson, Henry H.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Electrical properties of sub-100 nm SiGe nanowires2016Ingår i: Journal of semiconductors, Vol. 37, nr 10Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this study, the electrical properties of SiGe nanowires in terms of process and fabrication integrity, measurement reliability, width scaling, and doping levels were investigated. Nanowires were fabricated on SiGe-on oxide (SGOI) wafers with thickness of 52 nm and Ge content of 47%. The first group of SiGe wires was initially formed by using conventional I-line lithography and then their size was longitudinally reduced by cutting with a focused ion beam (FIB) to any desired nanometer range down to 60 nm. The other nanowires group was manufactured directly to a chosen nanometer level by using sidewall transfer lithography (STL). It has been shown that the FIB fabrication process allows manipulation of the line width and doping level of nanowires using Ga atoms. The resistance of wires thinned by FIB was 10 times lower than STL wires which shows the possible dependency of electrical behavior on fabrication method.

  • 3. Hu, Cheng
    et al.
    Xu, Peng
    Fu, Chaochao
    Zhu, Zhiwei
    Gao, Xindong
    Jamshidi, Asghar
    KTH, Skolan för informations- och kommunikationsteknik (ICT).
    Noroozi, Mohammad
    KTH, Skolan för informations- och kommunikationsteknik (ICT).
    Radamson, Henry
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Wu, Dongping
    Zhang, Shi-Li
    Characterization of Ni(Si,Ge) films on epitaxial SiGe(100) formed by microwave annealing2012Ingår i: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 101, nr 9, s. 092101-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Microwave annealing (MWA) is investigated as an alternative technique to rapid thermal processing with halogen lamp heating (RTP) for low-temperature silicide formation on epitaxially grown Si0.81Ge0.19 layers. Phase formation, resistivity mapping, morphology analysis, and composition evaluation indicate that the formation of low-resistivity NiSi1-xGex by means of MWA occurs at temperatures about 100 degrees C lower than by RTP. Under similar annealing conditions, more severe strain relaxation and defect generation are therefore found in the remaining Si0.81Ge0.19 layers treated by MWA. Although silicidation by microwave heating is in essence also due to thermal effects, details in heating mechanisms differ from RTP.

  • 4.
    Jamshidi, Asghar
    et al.
    KTH.
    Noroozi, Mohammad
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Material- och nanofysik, Funktionella material, FNM.
    Moeen, M.
    Hallén, Anders
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Hamawandi, Bejan
    KTH.
    Lu, J.
    Hultman, L.
    Östling, Mikael
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Radamson, Henry
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Growth of GeSnSiC layers for photonic applications2013Ingår i: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 230, s. 106-110Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This work presents epitaxial growth of intrinsic and doped GeSnSiC layers using Ge2H6, SnCl4, CH3SiH3, B2H6, PH3 and Si2H6 deposited at 290-380 degrees C on strain relaxed Ge buffer layer or Si substrate by using reduced pressure chemical vapor deposition (RPCVD) technique. The GeSnSi layers were compressively strained on Ge buffer layer and strain relaxed on Si substrate. It was demonstrated that the quality of epitaxial layers is dependent on the growth parameters and that the Sn content in epi-layers could be tailored by growth temperature. The Sn segregation caused surface roughness which was decreased by introducing Si and Si-C into Ge layer. The Sn content in GeSn was carefully determined from the mismatch, both parallel and perpendicular, to the growth direction when the Poisson ratio was calculated for a certain Ge-Sn composition. The X-ray results were excellently consistent with Rutherford Backscattered Spectroscopy (RBS). Strain relaxed GeSn layers were also used as virtual substrate to grow tensile-strained Ge layers. The Ge cap layer had low defect density and smooth surface which makes it a viable candidate material for future photonic applications.

  • 5.
    Noroozi, Mohammad
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Material- och nanofysik, Funktionella material, FNM.
    Growth, processing and characterization of group IV materials for thermoelectric applications2016Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Discover of new energy sources and solutions are one of the important global issues nowadays, which has a big impact on economy as well as environment. One of the methods to help to mitigate this issue is to recover wasted heat, which is produced in large quantities by the industry, through vehicle exhausts and in many other situations where we consume energy. One way to do this would be using thermoelectric (TE) materials, which enable direct interconversion between heat and electrical energy. This thesis investigates how the novel material combinations and nanotechnology could be used for fabricating more efficient TE materials and devices.

    The work presents synthesis, processing, and electrical characterization of group IV materials for TE applications. The starting point is epitaxial growth of alloys of group IV elements, silicon (Si), germanium (Ge) and tin (Sn), with a focus on SiGe and GeSn(Si) alloys. The material development is performed using chemical vapor deposition (CVD) technique. Strained and strain-relaxed Ge1-x Snx (0.01≤x≤0.15) has been successfully grown on Ge buffer and Si substrate, respectively. It is demonstrated that a precise control of temperature, growth rate, Sn flow and buffer layer quality is necessary to overcome Sn segregation and achieve a high quality GeSn layer. The incorporation of Si and n- and p-type dopant atoms is also investigated and it was found that the strain can be compensated in the presence of Si and dopant atoms. 

    Si1-xGexlayers are grown on Si-on-insulator wafers and condensed by oxidation at 1050 ᵒC to manufacture SiGe-on-insulator (SGOI) wafers. Nanowires (NWs) are processed, either by sidewall transfer lithography (STL), or by using conventional lithography, and subsequently manufactured into nanoscale dimensions by focused ion beam (FIB) technique. The NWs are formed in an array, where one side is heated by a resistive heater made of Ti/Pt. The power factor of NWs is measured and the results are compared for NWs manufactured by different methods. It is found that the electrical properties of NWs fabricated with FIB technique can be influenced due to Ga doping during ion milling.

    Finally, the carrier transport in SiGe NWs formed on SGOI samples is tailored by applying a back-gate voltage on the Si substrate. In this way, the power factor is improved by a factor of 4. This improvement is related to the presence of defects and/or small fluctuation of nanowire shape and Ge content along the NWs, generated during processing and condensation of SiGe layers. The SiGe results open a new window for operation of SiGe NWs-based TE devices in the new temperature range of 250 to 450 K.

  • 6.
    Noroozi, Mohammad
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Material- och nanofysik, Funktionella material, FNM.
    Abedin, Ahmad
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Moeen, Mahdi
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Östling, Mikael
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Radamson, Henry H.
    CVD growth of GeSnSiC alloys using disilane, digermane, tin tetrachloride and methylsilane2014Ingår i: ECS Transactions, 2014, Vol. 64, nr 6, s. 703-710Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this study, Ge1-x-y-zSnxSiyCz layers (0.01≤x≤ 0.06, 0≤y≤0.02 and 0≤z≤0.01) have been successfully grown at 280-330 °C on Ge and Si by using RPCVD technique. It was demonstrated that the quality of epitaxial layers is dependent on the growth parameters, layer thickness and the quality of Ge virtual layer. It was found that a proper strain balance in the matrix during the epitaxy where the Si is adjusted carefully with the Sn flux improves the incorporation of Sn in Ge matrix. A similar improvement of Sn incorporation has been observed for phosphorous, boron and carbon doping in GeSn layers as well. This is explained by the compensation of the compressive strain caused by Snand the tensile strain induced by Si to obtain the minimum energy in Ge matrix. This behavior was not observed for relaxed GeSn layers and Sn incorporation could be controlled only by the growth parameters. The thermal stability of GeSn is an important integration issue for device fabrication. The thermal stability of P- and B-doped GeSn layers was studied by rapid thermal annealing (RTA) in range of 400-600 °C and compared with intrinsic layers. The GeSn layers were stable up to 550 °C while the B-doped layers showed strain relaxation readily at 500 °C. The epitaxial quality of epi-layers was evaluated in terms of oxygen and water vapor contamination. The level of oxygen during epitaxy was as low as 10 ppb and the contamination amount was found as low as 1017 cm-3.

  • 7.
    Noroozi, Mohammad
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Material- och nanofysik, Funktionella material, FNM.
    Ergül, Adem
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Material- och nanofysik, Funktionella material, FNM.
    Abedin, Ahmed
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Toprak, Muhammet S
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik (Stängd 20120101), Funktionella material, FNM (Stängd 20120101).
    Radamson, Henry
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Fabrications of size-controlled SiGe nanowires using I-line lithography and focused ion beam technique2014Ingår i: ECS Transactions, 2014, nr 6, s. 167-174Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this study, a novel method using Focus Ion Beam (FIB) technique was applied to scale down Si1-xGex wires (x=0.27-0.57) to 20 nm width. Originally, the wires were processed by using Iline lithography and dry etching of SiGe on oxide (SGOI) substrates. The SGOI wafers were processed through condensation method where a SiGe/Si layer was grown in the beginning on SOI wafers and oxidized at 850-1050 °C. The shape of the nanowires (NWs) during the successive FIB cutting was examined by scanning electron microscopy (SEM) and the carrier transport through the NWs was checked by resistivity measurements. The contact resistance was reduced by Ni-silicide prior to metallization. The fabricated NWs were also suspended by tilting FIB. The results present the limitations and challenges of FIB technique to create NWs for advanced sensors and transistors.

  • 8.
    Noroozi, Mohammad
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Material- och nanofysik, Funktionella material, FNM.
    Hamawandi, Bejan
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Material- och nanofysik, Funktionella material, FNM.
    Jayakumar, Ganesh
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Material- och nanofysik, Funktionella material, FNM.
    Zahmatkesh, Katayoun
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Material- och nanofysik, Funktionella material, FNM.
    Radamson, Henry H.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Toprak, Muhammet S.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Material- och nanofysik, Funktionella material, FNM.
    A comparison of power factor in n and p-type SiGe nanowires for thermoelectric applications2017Ingår i: Journal of Nanoscience and Nanotechnology, ISSN 1533-4880, E-ISSN 1533-4899, Vol. 71, nr 3, s. 1622-1626Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This work presents the thermoelectric properties of n- and p-type doped SiGe nanowires and shows the potential to generate electricity from heat difference over nanowires. The Si0.74Ge0.26 layers were grown by reduced pressure chemical vapor deposition technique on silicon on insulator and were condensed to the final Si0.53Ge0.47 layer with thickness of 52 nm. The nanowires were formed by using sidewall transfer lithography (STL) technique at a targeted width of 60 nm. A high volume of NWs is produced per wafer in a time efficient manner and with high quality using this technique. The results demonstrate high Seebeck coefficient in both n- and p-types SiGe nanowires. N-type SiGe nanowires show significantly higher Seebeck coefficient and power factor compared to p-type SiGe nanowires near room temperature. These results are promising and the devised STL technique may pave the way to apply a Si compatible process for manufacturing SiGe-based TE modules for industrial applications.

  • 9.
    Noroozi, Mohammad
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Material- och nanofysik, Funktionella material, FNM.
    Hamawandi, Bejan
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Material- och nanofysik.
    Toprak, Muhammet S.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Material- och nanofysik, Funktionella material, FNM.
    Radamson, Henry H.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Fabrication and thermoelectric characterization of GeSn nanowires2014Ingår i: 2014 15th International Conference on Ultimate Integration on Silicon, ULIS 2014, IEEE Computer Society, 2014, s. 125-128Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this study, GeSn nanowires (NWs) were fabricated and the thermoelectric performance in terms of power factor and contact resistance have been investigated and compared to Ge and Si. The ohmic contact to the NWs was made by Pt/Ti whereas low contact resistance was obtained by Ni-GeSn (or Ni-Ge) layers. A detailed investigation was performed to process towards low resistance Ni-GeSn phase for GeSn NWs. The phase formation of Ni-GeSn layers was examined by x-ray diffraction (XRD) and the residual strain in GeSn beneath the Ni-GeSn was also measured by high resolution reciprocal lattice mapping (HRRLM). It was demonstrated that Ni reaction with GeSn layer resulted in strain reduction in the remained GeSn material due to Ni outdiffusion to the GeSn NWs demonstrated higher Seebeck coefficient compared to Ge and Si NWs, which suggest promising thermoelectric properties in GeSn.

  • 10.
    Noroozi, Mohammad
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Material- och nanofysik, Funktionella material, FNM.
    Jamshidi, Asghar
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Östling, Mikael
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Radamson, Henry
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Growth of GeSnSi Alloys by Reduced Pressure CVDManuskript (preprint) (Övrigt vetenskapligt)
  • 11.
    Noroozi, Mohammad
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Material- och nanofysik, Funktionella material, FNM.
    Jayakumar, Ganesh
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Lu, Jun
    Mensi, Mounir
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Material- och nanofysik, Optik och Fotonik, OFO.
    Hamawandi, Bejan
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Material- och nanofysik, Funktionella material, FNM.
    Zahmatkesh, Katayoun
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Material- och nanofysik, Funktionella material, FNM.
    Tafti, Mohsen. Y
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Material- och nanofysik, Funktionella material, FNM.
    Marcinkevičius, Saulius
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Material- och nanofysik, Optik och Fotonik, OFO.
    Hultman, Lars
    Ergül, Adem
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Material- och nanofysik, Funktionella material, FNM.
    Ikonic, Zoran
    Toprak, Muhammet S.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Material- och nanofysik, Funktionella material, FNM.
    Radamson, Henry H.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Significant Improvement of Thermoelectric Efficiency in SiGe NanowiresArtikel i tidskrift (Refereegranskat)
    Abstract [en]

    The thermoelectric (TE) properties of SiGe nanowires (NWs) with width of 60 nm in a back-gate configuration have been studied experimentally and theoretically. The carrier transport in NWs was modified by biasing voltage to the gate for different temperatures. The original wafers were SiGe-on-oxide (SGOI), which were formed through condensation of SiGe on Si-on-oxide wafers (SOI).  The power factor of SiGe NWs was enhanced by a factor of >2 in comparison with SiGe bulk material over a temperature range of 273 K to 450 K. This enhancement is mainly attributed to the energy filtering of carriers in SiGe NWs which were introduced by the roughness in the shape of NWs, non-uniform SiGe composition and the induced defects during the manufacturing of SGOI wafers or processing of NWs. These defects create potential barriers which may significantly enhance the Seebeck coefficient, while the conductivity can be boosted by tuning the back-gate bias.

  • 12.
    Noroozi, Mohammad
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik. Linköping University, Sverige.
    Jayakumar, Ganesh
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Elektronik, Integrerade komponenter och kretsar.
    Zahmatkesh, Katayoun
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik.
    Lu, J.
    Hultman, L.
    Mensi, Mounir
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik.
    Marcinkevicius, Saulius
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik.
    Hamawandi, Bejan
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Yakhshi Tafti, Mohsen
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik.
    Ergül, Adem
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik.
    Ikonic, Z.
    Toprak, Muhammet
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Biomedicinsk fysik och röntgenfysik.
    Radamson, Henry H.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Elektronik, Integrerade komponenter och kretsar.
    Unprecedented thermoelectric power factor in SiGe nanowires field-effect transistors2017Ingår i: ECS Journal of Solid State Science and Technology, ISSN 2162-8769, E-ISSN 2162-8777, Vol. 6, nr 9, s. Q114-Q119Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this work, a novel CMOS compatible process for Si-based materials has been presented to form SiGe nanowires (NWs) on SiGe On Insulator (SGOI) wafers with unprecedented thermoelectric (TE) power factor (PF). The TE properties of SiGe NWs were characterized in a back-gate configuration and a physical model was applied to explain the experimental data. The carrier transport in NWs was modified by biasing voltage to the gate at different temperatures. The PF of SiGe NWs was enhanced by a factor of >2 in comparison with bulk SiGe over the temperature range of 273 K to 450 K. This enhancement is mainly attributed to the energy filtering of carriers in SiGe NWs, which were introduced by imperfections and defects created during condensation process to form SiGe layer or in NWs during the processing of NWs.

  • 13.
    Noroozi, Mohammad
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Material- och nanofysik, Funktionella material, FNM.
    Moeen, Mahdi
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar. Nocilis Materials, Sweden .
    Abedin, Ahmad
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Toprak, Muhammet S.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Material- och nanofysik, Funktionella material, FNM.
    Radamson, Henry H.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Effect of strain on Ni-(GeSn)x contact formation to GeSn nanowires2014Ingår i: Materials Research Society Symposium Proceedings, 2014, Vol. 1707Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this study, the formation of Ni-(GeSn)x on strained and relaxed Ge1-xSnx (0.01≤x≤ 0.03) nanowires in contact areas has been investigated. The epi-layers were grown at different temperatures (290 to 380°C) by RPCVD technique. The strain in GeSn layers tailored through carefully chosen of growth parameters and virtual substrate. The nanowires were fabricated through both I-line and dry-etching. 15 nm Ni was deposited either on the contact areas or whole length of nanowires. The wires went through rapid thermal annealing at intervals of 360 to 550°C for 30s in N2 ambient. The results show the thermal stability and amount of particular phases were strain-dependent. The formation of Ni-GeSn was eased when GeSn layers were strain-free. When the Sn content is high the epi-layers suffer from Sn segregation. The Sn-rich surface impedes remarkably the Ni diffusion. The electrical conductivity measurement of nanowires shows low resistivity and Ohmic contact are obtained for Ni-GeSn.

  • 14.
    Radamson, Henry H.
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Noroozi, Mohammad
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Jamshidi, Asghar
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Thompson, P. E.
    Östling, Mikael
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Integrerade komponenter och kretsar.
    Strain engineering in GeSnSi materials2012Ingår i: SiGe, Ge, and related compounds 5: materials, processing, and devices, Electrochemical Society, 2012, nr 9, s. 527-531Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this study, Ge1-x-ySnxSiy layers (0.01≤x≤ 0.06 and 0≤y≤0.12) using Ge2H6, SnCl4 (SnD4) and Si2H6 have successfully grown at 290-310 °C on Ge virtual layer on Si(100) by using RPCVD technique. It has been demonstrated that the quality of epitaxial layers is dependent on the growth parameters, layer thickness and the quality of Ge virtual layer. The incorporation of P and B in GeSn matrix has been studied and the effect of dopant specie and concentration on Sn content has been presented. It was found that a proper balance of P, B or Si and Sn flux during the epitaxy improves the incorporation of Sn in Ge matrix. This is explained by the compensation of tensile strain induced by dopants or Si with the compressive strain caused by Sn to obtain the minimum energy in Ge matrix. P-i-n type doped structures of Ge-Sn-Si were grown and the layer quality was analyzed.

  • 15.
    Yakhshi Tafti, Mohsen
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Material- och nanofysik.
    Ballikaya, Sedat
    Khachatourian, Adrine Malek
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Material- och nanofysik.
    Noroozi, Mohammad
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Material- och nanofysik.
    Saleemi, Mohsin
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Material- och nanofysik.
    Han, Li
    Nong, Ngo V.
    Bailey, Trevor
    Uher, Ctirad
    Toprak, Muhammet S.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Material- och nanofysik.
    Promising bulk nanostructured Cu2Se thermoelectrics via high throughput and rapid chemical synthesis2016Ingår i: RSC ADVANCES, ISSN 2046-2069, Vol. 6, nr 112, s. 111457-111464Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A facile and high yield synthesis route was developed for the fabrication of bulk nanostructured copper selenide (Cu2Se) with high thermoelectric efficiency. Starting from readily available precursor materials and by means of rapid and energy-efficient microwave-assisted thermolysis, nanopowders of Cu2Se were synthesized. Powder samples and compacted pellets have been characterized in detail for their structural, microstructural and transport properties. alpha to beta phase transition of Cu2Se was confirmed using temperature dependent X-ray powder diffraction and differential scanning calorimetry analyses. Scanning electron microscopy analysis reveals the presence of secondary globular nanostructures in the order of 200 nm consisting of <50 nm primary particles. High resolution transmission electron microscopy analysis confirmed the highly crystalline nature of the primary particles with irregular truncated morphology. Through a detailed investigation of different parameters in the compaction process, such as applied load, heating rate, and cooling profiles, pellets with preserved nanostructured grains were obtained. An applied load during the controlled cooling profile was demonstrated to have a big impact on the final thermoelectric efficiency of the consolidated pellets. A very high thermoelectric figure of merit (ZT) above 2 was obtained at 900 K for SPS-compacted Cu2Se nanopowders in the absence of the applied load during the controlled cooling step. The obtained ZT exceeds the state of the art in the temperature ranges above phase transition, approaching up to 25% improvement at 900 K. The results demonstrate the prominent improvement in ZT attributed both to the low thermal conductivity, as low as 0.38 W m(-1) K-1 at 900 K, and the enhancement in the power factor of nanostructured Cu2Se. The proposed synthesis scheme as well as the consolidation could lead to reliable production of large scale thermoelectric nanopowders for niche applications.

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