| 1. |
- Luo, Jun, et al.
(författare)
-
Surface-energy triggered phase formation and epitaxy in nanometer-thick Ni1-xPtx silicide films
- 2010
-
Ingår i: APPLIED PHYSICS LETTERS. - 0003-6951. ; 96:3, s. 031911
-
Tidskriftsartikel (refereegranskat)abstract
- The formation of ultrathin silicide films of Ni1-xPtx at 450-850 degrees C is reported. Without Pt (x=0) and for t(Ni)andlt; 4 nm, epitaxially aligned NiSi2-y films readily grow and exhibit extraordinary morphological stability up to 800 degrees C. For t(Ni)andgt;= 4 nm, polycrystalline NiSi films form and agglomerate at lower temperatures for thinner films. Without Ni (x=1) and for t(Pt)=1-20 nm, the annealing behavior of the resulting PtSi films follows that for the NiSi films. The results for Ni1-xPtx of other compositions support the above observations. Surface energy is discussed as the cause responsible for the distinct behavior in phase formation and morphological stability.
|
|
| 2. |
- Gunnarsson Sarius, Niklas, 1976-, et al.
(författare)
-
Contact Resistance of Ti-Si-C-Ag and Ti-Si-C-Ag-Pd Nanocomposite Coatings
- 2012
-
Ingår i: Journal of Electronic Materials. - Springer. - 0361-5235. ; 41:3, s. 560-567
-
Tidskriftsartikel (refereegranskat)abstract
- Ti-Si-C-Ag-Pd and Ti-Si-C-Ag nanocomposite coatings were deposited by direct-current magnetron sputtering on Cu substrates with an electroplated Ni layer. Analytical electron microscopy, x-ray diffraction, and x-ray photoelectron spectroscopy show that the nanocomposites consist of TiC, Ag:Pd, and amorphous SiC. The contact resistance of these coatings against a spherical Au-Co surface was measured for applied contact forces up to 5 N. Ti-Si-C-Ag-Pd coatings with Ag:Pd top coating had ~10 times lower contact resistance at contact forces below 1 N (~10 mΩ at ~0.1 N), and 2 to 3 times lower for contact forces around 5 N (<1 mΩ at 5 N), compared with the Ti-Si-C-Ag coating.
|
|
| 3. |
- Lu, Jun, et al.
(författare)
-
On Epitaxy of Ultrathin Ni1-xPtx Silicide Films on Si(001)
- 2010
-
Ingår i: ELECTROCHEMICAL AND SOLID STATE LETTERS. - Electrochemical Society and Institute of Electronics Engineers. - 1099-0062. ; 13:10, s. H360-H362
-
Tidskriftsartikel (refereegranskat)abstract
- Epitaxial Ni(Pt)Si2-y (y andlt; 1) films readily grow upon thermal treatment of 2 nm thick Ni and Ni0.96Pt0.04 films deposited on Si(001). For annealing at 500 degrees C, the films are 5.4-5.6 nm thick with 61-70 mu cm in resistivity. At 750 degrees C, the epitaxial Ni(Pt)Si2-y films become 6.1-6.2 nm thick with a resistivity of 42-44 mu cm. Structural analysis reveals twins, facet wedges, and thickness inhomogeneities in the films grown at 500 degrees C. For higher temperature, an almost defect-free NiSi2-y film with a flat and sharp interface is formed. The presence of Pt makes the aforementioned imperfections more persistent.
|
|
| 4. |
- Luo, Jun, et al.
(författare)
-
On Different Process Schemes for MOSFETs With a Controllable NiSi-Based Metallic Source/Drain
- 2011
-
Ingår i: IEEE Transactions on Electron Devices. - 0018-9383. ; 58:7, s. 1898-1906
-
Tidskriftsartikel (refereegranskat)abstract
- This paper focuses on different silicidation schemes toward a controllable NiSi-based metallic source/drain (MSD) process with restricted lateral encroachment of NiSi. These schemes include thickness control of Ni, Ni-Pt alloying, and two-step annealing. Experimental results show that all the three process schemes can give rise to effective control of lateral encroachment during Ni silicidation. By controlling t(Ni), NiSi-based MSD metal-oxide-semiconductor field-effect transistors (MOSFETs) of gate length L-G = 55 nm are readily realized on ultrathin-body silicon-on-insulator substrates with 20-nm surface Si thickness. With the aid of dopant segregation (DS) to modifying the Schottky barrier heights of NiSi, both n- and p-type MSD MOSFETs show significant performance improvement, compared to reference devices without DS.
|
|
| 5. |
- Magnuson, Martin, et al.
(författare)
-
Electronic structure investigation of Ti3AlC2 , Ti3SiC2 , and Ti3GeC2 by soft x-ray emission spectroscopy
- 2005
-
Ingår i: Physical Review B Condensed Matter. - 0163-1829. ; 72:24, s. 245101
-
Tidskriftsartikel (refereegranskat)abstract
- The electronic structures of epitaxially grown films of Ti3AlC2 , Ti3SiC2 , and Ti3GeC2 have been investigated by bulk-sensitive soft x-ray emission spectroscopy. The measured high-resolution Ti L , C K , Al L , Si L , and Ge M emission spectra are compared with ab initio density-functional theory including core-to-valence dipole matrix elements. A qualitative agreement between experiment and theory is obtained. A weak covalent Ti-Al bond is manifested by a pronounced shoulder in the Ti L emission of Ti3AlC2 . As Al is replaced with Si or Ge, the shoulder disappears. For the buried Al and Si layers, strongly hybridized spectral shapes are detected in Ti3AlC2 and Ti3SiC2 , respectively. As a result of relaxation of the crystal structure and the increased charge-transfer from Ti to C, the Ti-C bonding is strengthened. The differences between the electronic structures are discussed in relation to the bonding in the nanolaminates and the corresponding change of materials properties.
|
|
| 6. |
- Berlind, Torun, 1965-, et al.
(författare)
-
Protein adsorption on thin films of carbon and carbon nitride monitored with in situ ellipsometry
- 2011
-
Ingår i: ACTA BIOMATERIALIA. - Elsevier Science B.V. Amsterdam. - 1742-7061. ; 7:3, s. 1369-1378
-
Tidskriftsartikel (refereegranskat)abstract
- Amorphous carbon and amorphous, graphitic and fullerene-like carbon nitride thin filmswere deposited by reactive magnetron sputtering and optically characterized withspectroscopic ellipsometry. The films were exposed to human serum albumin and theadsorption was monitored in situ using dynamic ellipsometry. From the ellipsometric data theadsorbed amount of proteins was quantified in terms of surface mass density using de Feijter'smodel. The results indicated larger adsorption of proteins onto the amorphous films comparedto the films with a more ordered microstructure. Complementary studies with labeled HSAusing radioimmunoassay showed up to 6 times higher protein adsorption compared to theellipsometry measurement which partly might be explained by differences in surfaceroughness (from 0.3 to 13 nm) among the films. The elutability of adsorbed labeled HSAusing unlabeled HSA and sodium dodecyl sulphate was low compared to a silicon reference.In addition, the four types of films were incubated in blood plasma followed by antifibrinogen,anti-HMWK or anti-C3c revealing the materials response to complement andcontact activation. Three of the films indicated immunoactivity, whereas the amorphouscarbon showed less immunoactivity compared to a titanium reference. All films showedindications of a stronger ability to initiate the intrinsic pathway of coagulation, compared tothe reference. Finally, the surfaces bone bonding ability was investigated by examination oftheir ability to form calcium phosphate (CaP) crystals in a simulated body fluid, with a-CNxdepositing most CaP after 21 days of incubation.
|
|
| 7. |
- Buchholt, Kristina, et al.
(författare)
-
Ohmic contact properties of magnetron sputtered Ti3SiC2 on n- and p-type 4H-silicon carbide
- 2011
-
Ingår i: Applied Physics Letters. - American Institute of Physics. - 0003-6951. ; 98:4, s. 042108
-
Tidskriftsartikel (refereegranskat)abstract
- Epitaxial Ti3SiC2 (0001) thin film contacts were grown on doped 4H-SiC (0001) using magnetron sputtering in an ultra high vacuum system. The specific contact resistance was investigated using linear transmission line measurements. Rapid thermal annealing at 950 degrees C for 1 min of as-deposited films yielded ohmic contacts to n-type SiC with contact resistances in the order of 10(-4) Omega cm(2). Transmission electron microscopy shows that the interface between Ti3SiC2 and n-type SiC is atomically sharp with evidence of interfacial ordering after annealing.
|
|
| 8. |
- Eklund, Per, et al.
(författare)
-
Discovery of the Ternary Nanolaminated Compound Nb2GeC by a Systematic Theoretical-Experimental Approach
- 2012
-
Ingår i: Physical Review Letters. - American Physical Society. - 0031-9007. ; 109:3, s. 035502
-
Tidskriftsartikel (refereegranskat)abstract
- Since the advent of theoretical materials science some 60 years ago, there has been a drive to predict and design new materials in silicio. Mathematical optimization procedures to determine phase stability can be generally applicable to complex ternary or higher-order materials systems where the phase diagrams of the binary constituents are sufficiently known. Here, we employ a simplex-optimization procedure to predict new compounds in the ternary Nb-Ge-C system. Our theoretical results show that the hypothetical Nb2GeC is stable, and excludes all reasonably conceivable competing hypothetical phases. We verify the existence of the Nb2GeC phase by thin film synthesis using magnetron sputtering. This hexagonal nanolaminated phase has a and c lattice parameters of similar to 3.24 angstrom and 12.82 angstrom.
|
|
| 9. |
- Eklund, Per, et al.
(författare)
-
Structural, electrical, and mechanical properties of nc-TiC/a-SiC nanocomposite thin films
- 2005
-
Ingår i: Journal of Vacuum Science & Technology B. - 1071-1023. ; 23:6, s. 2486-2495
-
Tidskriftsartikel (refereegranskat)abstract
- We have synthesized Ti–Si–C nanocomposite thin films by dc magnetron sputtering from a Ti3SiC2 compound target in an Ar discharge on Si(100), Al2O3(0001), and Al substrates at temperatures from room temperature to 300 °C. Electron microscopy, x-ray diffraction, and x-ray photoelectron spectroscopy showed that the films consisted of nanocrystalline (nc-) TiC and amorphous (a-) SiC, with the possible presence of a small amount of noncarbidic C. The growth mode was columnar, yielding a nodular film-surface morphology. Mechanically, the films exhibited a remarkable ductile behavior. Their nanoindentation hardness and E-modulus values were 20 and 290 GPa, respectively. The electrical resistivity was 330 µ<img src="http://scitation.aip.org/stockgif3/OHgr.gif" /> cm for optimal Ar pressure (4 mTorr) and substrate temperature (300 °C). The resulting nc-TiC/a-SiC films performed well as electrical contact material. These films' electrical-contact resistance against Ag was remarkably low, 6 µ<img src="http://scitation.aip.org/stockgif3/OHgr.gif" /> at a contact force of 800 N compared to 3.2 µ<img src="http://scitation.aip.org/stockgif3/OHgr.gif" /> for Ag against Ag. The chemical stability of the nc-TiC/a-SiC films was excellent, as shown by a Battelle flowing mixed corrosive-gas test, with no N, Cl, or S contaminants entering the bulk of the films.
|
|
| 10. |
- Eklund, Per, et al.
(författare)
-
The Mn + 1AXn phases
- 2010
-
Ingår i: Thin Solid Films. - 0040-6090. ; 518:8, s. 1851-1878
-
Forskningsöversikt (refereegranskat)abstract
- This article is a Critical review of the M(n + 1)AX(n) phases ("MAX phases", where n = 1, 2, or 3) from a materials science perspective. MAX phases are a class of hexagonal-structure ternary carbides and nitrides ("X") of a transition metal ("M") and an A-group element. The most well known are Ti2AlC, Ti3SiC2, and Ti4AlN3. There are similar to 60 MAX phases with at least 9 discovered in the last five years alone. What makes the MAX phases fascinating and potentially useful is their remarkable combination of chemical, physical, electrical, and mechanical properties, which in many ways combine the characteristics of metals and ceramics. For example, MAX phases are typically resistant to oxidation and corrosion, elastically stiff, but at the same time they exhibit high thermal and electrical conductivities and are machinable. These properties stem from an inherently nanolaminated crystal structure, with M1 + nXn slabs intercalated with pure A-element layers. The research on MAX phases has been accelerated by the introduction of thin-film processing methods. Magnetron sputtering and arc deposition have been employed to synthesize single-crystal material by epitaxial growth, which enables studies of fundamental material properties. However, the surface-initiated decomposition of M(n + 1)AX(n) thin films into MX compounds at temperatures of 1000-1100 degrees C is much lower than the decomposition temperatures typically reported for the corresponding bulk material. We also review the prospects for low-temperature synthesis, which is essential for deposition of MAX phases onto technologically important substrates. While deposition of MAX phases from the archetypical Ti-Si-C and Ti-Al-N systems typically requires synthesis temperatures of similar to 800 degrees C, recent results have demonstrated that V2GeC and Cr2AlC can be deposited at similar to 450 degrees C. Also, thermal spray of Ti2AlC powder has been used to produce thick coatings. We further treat progress in the use of first-principle calculations for predicting hypothetical MAX phases and their properties. Together with advances in processing and materials analysis, this progress has led to recent discoveries of numerous new MAX phases such as Ti4SiC3, Ta4AlC3. and Ti3SnC2. Finally, important future research directions are discussed. These include charting the unknown regions in phase diagrams to discover new equilibrium and metastable phases, as well as research challenges in understanding their physical properties, such as the effects of anisotropy, impurities, and vacancies on the electrical properties, and unexplored properties such as Superconductivity, magnetism, and optics.
|
|
