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Ghafoor, Naureen
Publications (10 of 40) Show all publications
Ghafoor, N., Eriksson, F., Andrew, A., Gullikson, E., Franz, S., Greczynski, G. & Birch, J. (2017). Impact of B4C co-sputtering on structure and optical performance of Cr/Sc multilayer X-ray mirrors. Optics Express, 25(15), 18274-18287
Open this publication in new window or tab >>Impact of B4C co-sputtering on structure and optical performance of Cr/Sc multilayer X-ray mirrors
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2017 (English)In: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 25, no 15, p. 18274-18287Article in journal (Refereed) Published
Abstract [en]

The influence of B4C incorporation during magnetron sputter deposition of Cr/Sc multilayers intended for soft X-ray reflective optics is investigated. Chemical analysis suggests formation of metal: boride and carbide bonds which stabilize an amorphous layer structure, resulting in smoother interfaces and an increased reflectivity. A near-normal incidence reflectivity of 11.7%, corresponding to a 67% increase, is achieved at λ = 3.11 nm upon adding 23 at.% (B + C). The advantage is significant for the multilayer periods larger than 1.8 nm, where amorphization results in smaller interface widths, for example, giving 36% reflectance and 99.89% degree of polarization near Brewster angle for a multilayer polarizer. The modulated ion-energy-assistance during the growth is considered vital to avoid intermixing during the interface formation even when B + C are added.

Place, publisher, year, edition, pages
Optical Society of America, 2017
National Category
Natural Sciences Inorganic Chemistry
Identifiers
urn:nbn:se:liu:diva-139944 (URN)10.1364/oe.25.018274 (DOI)000408584400128 ()28789315 (PubMedID)2-s2.0-85025823281 (Scopus ID)
Note

Funding agencies: Swedish Science Council; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University (Faculty Grant SFO-Mat-LiU) [2009 00971]

Available from: 2017-08-22 Created: 2017-08-22 Last updated: 2017-11-29Bibliographically approved
Barrirero, J., Li, J., Engstler, M., Ghafoor, N., Schumacher, P., Odén, M. & Muecklich, F. (2016). Cluster formation at the Si/liquid interface in Sr and Na modified Al-Si alloys. Scripta Materialia, 117, 16-19
Open this publication in new window or tab >>Cluster formation at the Si/liquid interface in Sr and Na modified Al-Si alloys
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2016 (English)In: Scripta Materialia, ISSN 1359-6462, E-ISSN 1872-8456, Vol. 117, p. 16-19Article in journal (Refereed) Published
Abstract [en]

Atom probe tomography was used to compare Na and Sr modified Al-Si hypoeutectic alloys. Both Na and Sr promote the formation of nanometre-sized clusters in the Si eutectic phase. Compositional analyses of the clusters show an Al:Sr ratio of 2.92 +/- 0.46 and an Al:Na ratio of 1.07 +/- 0.23. It is proposed that SrAl2Si2 and NaAlSi clusters are formed at the Si/liquid interface and take part in the modification process by altering the eutectic Si growth.

Place, publisher, year, edition, pages
PERGAMON-ELSEVIER SCIENCE LTD, 2016
Keywords
Eutectic solidification; Atom probe tomography; Aluminium alloys; Eutectic modification; Transmission electron microscopy
National Category
Physical Sciences
Identifiers
urn:nbn:se:liu:diva-127548 (URN)10.1016/j.scriptamat.2016.02.018 (DOI)000373547500004 ()
Note

Funding Agencies|German Federal Ministry of Economics and Technology [AiF 17204 N]; European Regional Development Fund (AME-Lab) [C/4-EFRE-13/2009/Br]; German Research Foundation (DFG); Federal State Government of Saarland [INST 256/298-1 FUGG]; Erasmus Mundus Doctoral Programme DocMASE of the European Commission [FPA 2011-0020]; VINNOVA Strategic Faculty Grant VINNMER Marie Curie Chair [2011-03464]; Major International (Regional) Joint Research Project from China [51420105005]

Available from: 2016-05-04 Created: 2016-05-03 Last updated: 2019-09-13
Johnson, L., Ghafoor, N., Engberg, D., Thuvander, M., Stiller, K., Odén, M. & Hultman, L. (2016). Self-organized Nanostructuring in Zr0.64Al0.36N Thin Films Studied by Atom Probe Tomography. Thin Solid Films, 233-238
Open this publication in new window or tab >>Self-organized Nanostructuring in Zr0.64Al0.36N Thin Films Studied by Atom Probe Tomography
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2016 (English)In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, p. 233-238Article in journal (Refereed) Published
Abstract [en]

We have applied atom probe tomography (apt) to analyze the selforganized structure of wear-resistant Zr0.64Al0.36N thin films grown by magnetron sputtering. Transmission electron microscopy shows that these films grow as a two-dimensional nanocomposite, consisting of interleaved lamellae in a labyrinthine structure, with a size scale of ∼ 5 nm. The structure was recovered in the Al apt signal, while the Zr and N data lacked structural information due to severe local magnification effects. The onset of the self-organized growth was observed to occur locally by nucleation, at 5-8 nm from the MgO substrate, after increasing Zr-Al compositional fluctuations. Finally, it was observed that the self-organized growth mode could be perturbed by renucleation of ZrN.

Place, publisher, year, edition, pages
Elsevier, 2016
National Category
Natural Sciences
Identifiers
urn:nbn:se:liu:diva-84258 (URN)10.1016/j.tsf.2016.07.034 (DOI)000381939700037 ()
Note

Funding agencies: VINN Excellence Center on Functional Nanoscale Materials; Swedish Research Council; Swedish Government Strategic Faculty Grant in Materials Science (SFO Mat-LiU) at Linkoping University; Swedish Governmental Agency for Innovation Systems (Vinnova) [2011-0

Vid tiden för disputationen förelåg publikationen som manuskript

Available from: 2012-10-03 Created: 2012-10-03 Last updated: 2019-08-02Bibliographically approved
Schroeder, J., Thomson, W., Howard, B., Schell, N., Näslund, L.-Å., Rogström, L., . . . Birch, J. (2015). Industry-relevant magnetron sputtering and cathodic arc ultra-high vacuum deposition system for in situ x-ray diffraction studies of thin film growth using high energy synchrotron radiation. Review of Scientific Instruments, 86(9), 095113
Open this publication in new window or tab >>Industry-relevant magnetron sputtering and cathodic arc ultra-high vacuum deposition system for in situ x-ray diffraction studies of thin film growth using high energy synchrotron radiation
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2015 (English)In: Review of Scientific Instruments, ISSN 0034-6748, E-ISSN 1089-7623, Vol. 86, no 9, p. 095113-Article in journal (Refereed) Published
Abstract [en]

We present an industry-relevant, large-scale, ultra-high vacuum (UHV) magnetron sputtering and cathodic arc deposition system purposefully designed for time-resolved in situ thin film deposition/annealing studies using high-energy (greater than50 keV), high photon flux (greater than10(12) ph/s) synchrotron radiation. The high photon flux, combined with a fast-acquisition-time (less than1 s) two-dimensional (2D) detector, permits time-resolved in situ structural analysis of thin film formation processes. The high-energy synchrotron-radiation based x-rays result in small scattering angles (less than11 degrees), allowing large areas of reciprocal space to be imaged with a 2D detector. The system has been designed for use on the 1-tonne, ultra-high load, high-resolution hexapod at the P07 High Energy Materials Science beamline at PETRA III at the Deutsches Elektronen-Synchrotron in Hamburg, Germany. The deposition system includes standard features of a typical UHV deposition system plus a range of special features suited for synchrotron radiation studies and industry-relevant processes. We openly encourage the materials research community to contact us for collaborative opportunities using this unique and versatile scientific instrument. (C) 2015 AIP Publishing LLC.

Place, publisher, year, edition, pages
AMER INST PHYSICS, 2015
National Category
Physical Sciences
Identifiers
urn:nbn:se:liu:diva-122441 (URN)10.1063/1.4930243 (DOI)000362573300065 ()26429486 (PubMedID)
Note

Funding Agencies|Swedish Research Council via the Rontgen Angstrom Cluster (RAC) Frame Program [2011-6505]; German Federal Ministry of Education and Research (BMBF) [05K12CG1]

Available from: 2015-11-03 Created: 2015-11-02 Last updated: 2019-10-07
Ghafoor, N., Petrov, I., Klenov, D. O., Freitag, B., Jensen, J., Greene, J. E., . . . Odén, M. (2015). Self-organized anisotropic (Zr1-xSix)N-y nanocomposites grown by reactive sputter deposition. Acta Materialia, 82, 179-189
Open this publication in new window or tab >>Self-organized anisotropic (Zr1-xSix)N-y nanocomposites grown by reactive sputter deposition
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2015 (English)In: Acta Materialia, ISSN 1359-6454, E-ISSN 1873-2453, Vol. 82, p. 179-189Article in journal (Refereed) Published
Abstract [en]

The physical properties of hard and superhard nanocomposite thin films are strongly dependent on their nanostructure. Here, we present the results of an investigation of nanostructural evolution and the resulting mechanical properties of (Zr1-xSix)N-y films, with 0 less than= x less than= 1 and 1 less than= y less than= 1.27, grown on MgO(0 0 1) and Al2O3(0 0 0 1) substrates at temperatures T-s = 500-900 degrees C by reactive magnetron sputter deposition from Zr and Si targets. X-ray diffraction and transmission electron microscopy (TEM) results show that there is a T-s/composition window in which stoichiometric Zr-Si-N and amorphous a-Si3N4 phases mutually segregate and self-organize into encapsulated 3-5 um wide ZrN-rich (Zr1-xSix)N columns which extend along the growth direction with a strong (002) texture. Lattice-resolved scanning TEM and energy-dispersive X-ray spectroscopy reveal that the (Zr1-xSix)N-y nanocolumns are separated by a bilayer tissue phase consisting of a thin crystalline SiNy-rich (Zr1-xSix)N-y layer with an a-Si3N4 overlayer. Incorporation of metastable SiN into NaCl-structure ZrN leads to an enhanced nanoindentation hardness H which is a function of T-s and film composition. For nanocomposites with composition (Zr(0.8)Sio(0.2))N-1.14 (10 at.% Si) H, increases from 26 GPa at 500 degrees C to 37 GPa at 900 degrees C. For comparison, the hardness of epitaxial ZrN/MgO(0 0 1) layers grown at T-s = 800 degrees C is 24 GPa. (C) 2014 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Place, publisher, year, edition, pages
Elsevier, 2015
Keywords
ZrSiN nanocomposites; Magnetron sputtering; Self-organization; Nanoindentation; Hard coatings
National Category
Physical Sciences
Identifiers
urn:nbn:se:liu:diva-113717 (URN)10.1016/j.actamat.2014.09.029 (DOI)000347017800017 ()
Note

Funding Agencies|VINNOVA VINN Excellence Center on Functional Nanoscale Materials (FunMat); Swedish Research Council; Swedish Foundation of Strategic Research (SSF); Swedish Government Strategic Research Area Faculty Grant in Materials Science (SFO-Mat-LiU)

Available from: 2015-01-30 Created: 2015-01-29 Last updated: 2017-12-05
Rogström, L., Ghafoor, N., Schroeder, J., Schell, N., Birch, J., Ahlgren, M. & Odén, M. (2015). Thermal stability of wurtzite Zr1-xAlxN coatings studied by in situ high-energy x-ray diffraction during annealing. Journal of Applied Physics, 118(3), Article ID 035309.
Open this publication in new window or tab >>Thermal stability of wurtzite Zr1-xAlxN coatings studied by in situ high-energy x-ray diffraction during annealing
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2015 (English)In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 118, no 3, article id 035309Article in journal (Refereed) Published
Abstract [en]

We study the thermal stability of wurtzite (w) structure ZrAlN coatings by a combination of in situ high-energy x-ray scattering techniques during annealing and electron microscopy. Wurtzite structure Zr1-xAlxN coatings with Al-contents from x = 0.46 to x = 0.71 were grown by cathodic arc evaporation. The stability of the w-ZrAlN phase depends on chemical composition where the higher Al-content coatings are more stable. The wurtzite ZrAlN phase was found to phase separate through spinodal decomposition, resulting in nanoscale compositional modulations, i.e., alternating Al-rich ZrAlN layers and Zr-rich ZrAlN layers, forming within the hexagonal lattice. The period of the compositional modulations varies between 1.7 and 2.5 nm and depends on the chemical composition of the coating where smaller periods form in the more unstable, high Zr-content coatings. In addition, Zr leaves the w-ZrAlN lattice to form cubic ZrN precipitates in the column boundaries. (C) 2015 AIP Publishing LLC.

Place, publisher, year, edition, pages
American Institute of Physics (AIP), 2015
National Category
Physical Sciences
Identifiers
urn:nbn:se:liu:diva-120742 (URN)10.1063/1.4927156 (DOI)000358429200055 ()
Note

Funding Agencies|VINN Excellence Center on Functional Nanoscale Materials (FunMat); Rontgen-Angstrom Cluster [VR 2011-6505]

Available from: 2015-08-24 Created: 2015-08-24 Last updated: 2017-12-04
Kumar Yalamanchili, P., Schramm, I. C., Jimenez-Pique, E., Rogström, L., Muecklich, F., Odén, M. & Ghafoor, N. (2015). Tuning hardness and fracture resistance of ZrN/Zr0.63Al0.37N nanoscale multilayers by stress-induced transformation toughening. Acta Materialia, 89, 22-31
Open this publication in new window or tab >>Tuning hardness and fracture resistance of ZrN/Zr0.63Al0.37N nanoscale multilayers by stress-induced transformation toughening
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2015 (English)In: Acta Materialia, ISSN 1359-6454, E-ISSN 1873-2453, Vol. 89, p. 22-31Article in journal (Refereed) Published
Abstract [en]

Structure and mechanical properties of nanoscale multilayers of ZrN/Zr0.63Al0.37N grown by reactive magnetron sputtering on MgO (0 0 1) substrates at a temperature of 700 degrees C are investigated as a function of the Zr0.63Al0.37N layer thickness. The Zr0.63Al0.37N undergoes in situ chemical segregation into ZrN-rich and AlN-rich domains. The AlN-rich domains undergo transition from cubic to wurtzite crystal structure as a function of Zr0.63Al0.37N layer thickness. Such structural transformation allows systematic variation of hardness as well as fracture resistance of the films. A maximum fracture resistance is achieved for 2 nm thick Zr0.63Al0.37N layers where the AlN-rich domains are epitaxially stabilized in the metastable cubic phase. The metastable cubic-AlN phase undergoes stress-induced transformation to wurtzite-AlN when subjected to indentation, which results in the enhanced fracture resistance. A maximum hardness of 34 GPa is obtained for 10 nm thick Zr0.63Al0.37N layers where the wurtzite-AlN and cubic-ZrN rich domains form semi-coherent interfaces.

Place, publisher, year, edition, pages
Elsevier, 2015
Keywords
Nitride multilayer thin films; Mechanical properties; Fracture toughness
National Category
Physical Sciences
Identifiers
urn:nbn:se:liu:diva-118029 (URN)10.1016/j.actamat.2015.01.066 (DOI)000353249100003 ()
Note

Funding Agencies|European Unions Erasmus-Mundus graduate school in Material Science and Engineering (DocMASE); Swedish Foundation for Strategic Research (SSF) through the grant Designed Multicomponent Coatings (MultiFilms); Swedish Governmental Agency for Innovation Systems (Vinnova) through the VINN Excellence Centre FunMat; VINNMER Grant [2011-03464]; EU [C/4-EFRE-13/2009/Br]; DFG; federal state government of Saarland [INST 256/298-1 FUGG]

Available from: 2015-05-21 Created: 2015-05-20 Last updated: 2017-12-04Bibliographically approved
Forsén, R., Syed, M. B., Ghafoor, N. & Odén, M. (2014). Alloying as a tool for structure and thermal stability engineering of hard coatings.
Open this publication in new window or tab >>Alloying as a tool for structure and thermal stability engineering of hard coatings
2014 (English)Manuscript (preprint) (Other academic)
Abstract [en]

A large range of (ZrxAly Cr(100-x-y))1N1 coatings have been deposited using cathodic arc evaporation and annealed at temperatures up to 1100 ºC. The coatings can be divided into three different characteristic categories based on their structure, thermal stability and hardness.

The first category of coatings, (Al < ~30 % and ~40 % < Zr), are stable cubic solid solutions up to 1100 ºC. The hardness decreases upon annealing because of defect annihilation.

In the second category, (40 % < Al < 60 % and Zr < 15 %), the coatings decompose into ZrCr- and Al-rich nanometer-sized domains when annealed, which results in a hardness increase.

In the third category (~67 % < Al), the microstructure contain a mixture of 1-2 nanometer-sized nano-crystalline hexagonal (AlN) and cubic (ZrCrN) phases. These coatings have a significantly lower hardness in the as deposited state but upon annealing the hardness increases significantly.

National Category
Physical Sciences
Identifiers
urn:nbn:se:liu:diva-110683 (URN)
Available from: 2014-09-18 Created: 2014-09-18 Last updated: 2014-09-18Bibliographically approved
Ghafoor, N., Lind, H., Tasnadi, F., Abrikosov, I. & Odén, M. (2014). Anomalous epitaxial stability of (001) interfaces in ZrN/SiNx multilayers. APL Materials, 2(4), 046106
Open this publication in new window or tab >>Anomalous epitaxial stability of (001) interfaces in ZrN/SiNx multilayers
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2014 (English)In: APL Materials, ISSN 2166-532X, Vol. 2, no 4, p. 046106-Article in journal (Refereed) Published
Abstract [en]

Isostructural stability of B1-NaCl type SiN on (001) and (111) oriented ZrN surfaces is studied theoretically and experimentally. The ZrN/SiNx/ZrN superlattices with modulation wavelength of 3.76 nm (dSiNx similar to 0.4 nm) were grown by dc-magnetron sputtering on MgO(001) and MgO(111). The results indicate that 0.4 nm thin SiNx layers utterly influence the preferred orientation of epitaxial growth: on MgO(001) cube-on-cube epitaxy of ZrN/SiNx superlattices were realized whereas multilayers on MgO(111) surface exhibited an unexpected 002 texture with a complex fourfold 90 degrees-rotated in-plane preferred orientation. Density functional theory calculations confirm stability of a (001) interface with respect to a (111) which explains the anomaly.

Place, publisher, year, edition, pages
American Institute of Physics, 2014
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-107456 (URN)10.1063/1.4870876 (DOI)000336083600007 ()
Available from: 2014-06-12 Created: 2014-06-12 Last updated: 2015-03-16Bibliographically approved
Barrirero, J., Engstler, M., Ghafoor, N., de Jonge, N., Odén, M. & Muecklich, F. (2014). Comparison of segregations formed in unmodified and Sr-modified Al-Si alloys studied by atom probe tomography and transmission electron microscopy. Journal of Alloys and Compounds, 611, 410-421
Open this publication in new window or tab >>Comparison of segregations formed in unmodified and Sr-modified Al-Si alloys studied by atom probe tomography and transmission electron microscopy
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2014 (English)In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 611, p. 410-421Article in journal (Refereed) Published
Abstract [en]

The mechanical properties of Al-7 wt.% Si can be enhanced by structural modifications of its eutectic phase. Addition of low concentrations of certain elements, in this case 150 wt-ppm Sr, is enough to cause a transition from a coarse plate-like Si structure to a finer coralline one. To fully understand the operating mechanism of this modification, the composition of the eutectic Si phase in unmodified and Sr-modified alloys was analysed and compared by atom probe tomography and (scanning) transmission electron microscopy. The unmodified alloy showed nanometre sized Al-segregations decorating defects, while the Sr-modified sample presented three types of Al-Sr segregations: (1) rod-like segregations that promote smoothening of the Al-Si boundaries in the eutectic phase, (2) particle-like segregations comparable to the ones seen in the unmodified alloy, and (3) planar segregations favouring the formation of twin boundaries. Al and Sr solubilities in Si after solidification were determined to be 430 +/- 160 at-ppm and 40 +/- 10 at-ppm, respectively. Sr predominantly segregates to the Si phase confirming its importance in the modification of the eutectic growth.

Place, publisher, year, edition, pages
Elsevier, 2014
Keywords
Aluminium-silicon alloys; Strontium modification; Atom probe tomography; Transmission electron microscopy; Microstructure
National Category
Physical Sciences
Identifiers
urn:nbn:se:liu:diva-109356 (URN)10.1016/j.jallcom.2014.05.121 (DOI)000338932400064 ()
Available from: 2014-08-15 Created: 2014-08-15 Last updated: 2019-09-13Bibliographically approved
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