مجال
التميز
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تميز دراسي وبحثي
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البحوث المنشورة
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البحث (1):
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عنوان البحث:
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Nano-Scale
Movement Induced In Graphene Ripples by Multi-Probe Microscopy
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رابط إلى البحث:
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here
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تاريخ النشر:
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24/06/2017
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موجز عن البحث:
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An Omicron low temperature multi-probe
technique is used for manipulation of mechanically exfoliated suspended and
attached graphene sheets on SiO2 substrates. Scanning electron microscopy
(SEM) and Raman spectroscopy are used to detect the graphene sheets and
determine their thicknesses and quality, respectively. The interaction of the
etched tungsten tip with the graphene is used to lift and release the sheet
and induce artificial ripples. Both suspended and attached sheets onto the
substrates show different behaviour in response to bias voltage.
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البحث (2):
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عنوان البحث:
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Electron Beam Lithography and Plasma Etching To
Fabricate Supports for Studying Nanomaterials
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رابط إلى البحث:
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Click
here
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تاريخ النشر:
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24/06/2017
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موجز عن البحث:
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The fabrication
processes of different nano- structures by electron beam lithography (EBL)
and plasma dry etching are shown. The periodic circle and square patterns
with different sizes were defined in the resist by EBL and then formed in the
substrates by plasma etching. The holes were created with a diameter ranging
from 1um to 5um and an etch depth from around 500nm to 1um. The quality and
the size of fabricated patterns and their dependence on the etching time were
investigated using top-down and cross-sectional scanning electron microscopy
(SEM). It was found that the structures are well-resolved in the patterns
with high levels of quality and good size uniformity. The results show that
the depth of the structures does not depend on their size or geometry but
rather on the etch time.
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المؤتمرات العلمية:
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المؤتمر (1):
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عنوان المؤتمر:
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The 9th
Saudi Students’ Conference
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تاريخ الإنعقاد:
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13-14 February 2016
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مكان
الإنعقاد:
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Birmingham,
UK
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طبيعة المشاركة:
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Poster
Presentation
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عنوان المشاركة:
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Manipulation
of graphene sheets using a local electrostatic force
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ملخص المشاركة:
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Graphene has received much attention due to
its high strength, small mass and unique electronic properties, which make it
a strong candidate for nano-electromechanical systems. The first studies
examined graphene on substrates, but the interactions between graphene and
substrates can impart ripples on graphene, which reduce its intrinsic
mobility [1]. Recently, studies have been performed on ultra-flat substrates
or on suspended sheets over holes in order to obtain a better understanding
of its intrinsic properties[2]. However, recent studies show that graphene
has intrinsic ripples that are not induced by the substrate. These finding
suggest that the ripples appear if graphene is suspended over holes[1]. On
the other hand, recent simulations predict improved chemical activity in
corrugated graphene, which makes it a good candidate for sensor applications
[2]. In this work, an Omicron multi-probe system was used to manipulate graphene
sheets locally, guided under Scanning electron microscopy (SEM). The graphene
sample was prepared by mechanical exfoliation onto a prefabricated etched
silicon dioxide/silicon (SiO2/Si) substrate [3]. Electron beam lithography
was used to create arrays of square trenches on Si wafers and then 90 nm of a
SiO2 layer was grown thermally. SEM and Raman spectroscopy were used to
locate the few and multilayer suspended sheets and to determine the thickness
and quality of the sheets, respectively [4]. Nanoprobe measurements were
performed at room temperature on the few and multilayer suspended sheets, as
well as layers of the same sheets attached to the substrate. The
electrostatic interaction of the etched tungsten probe with the graphene is
used as a non-contact means to push and lift the sheets both as a group and
as individual sheets, to introduce artificial rippling and to separate out
single layers of graphene. Both suspended and on-substrate sheets exhibit
different behaviours and different voltagefield dependences.
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المؤتمر (2):
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عنوان المؤتمر:
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6th International Advances in Applied Physics and
Materials Science Congress & Exhibition
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تاريخ الإنعقاد:
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01-03 June 2016
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مكان
الإنعقاد:
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Istanbul,
Turkey
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طبيعة المشاركة:
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Oral
Presentation
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عنوان المشاركة:
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Displacement
measurements of graphene ripples induced using nanoscale two-probe
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ملخص المشاركة:
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The remarkable electronic and mechanical
properties of graphene continue to drive much research. This membrane is
naturally non-flat and contains nano-ripples even when suspended. Further
extrinsic rippling can be imparted to graphene when sitting on a substrate
due to the substrate–graphene interaction. Since rippling affects the
mechanical and electronic properties, there is an increasing need for understanding
and controlling the rippling deformation. This study shows manipulation and
measurement of ripples of few and multilayer suspended sheets, as well as
layers of the same sheets on the substrate using a multi-probe system.
Samples are prepared by mechanical exfoliation onto a patterned SiO2/Si
substrate and characterized using SEM, Raman spectroscopy and AFM. An Omicron
multi-probe system is used to manipulate graphene locally where two etched
tips are used; one to contact the sheet and provide ground and another to
perform the electrostatic manipulation experiments. This method allows a
processing-free electrical contact to be made to the pristine graphene which
reduces potential sources of impurities that arise when electrodes are formed
using lithography. We observe permanent ripples induced in both graphene
sheets as pulled and released by the biased tip. The displacement
measurements of these ripples show different voltage-field dependences,
allowing a new way to measure the mechanical and adhesion properties of
graphene.
This study shows that a multi-probe system
can be used to explore the mechanism of rippling deformation of graphene by
means of repulsive and attractive tip-sample interaction, which plays a vital
role in the development of graphene electronic devices.
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المؤتمر (3):
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عنوان المؤتمر:
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AEM2016:
8th International conference on Advanced Nanomaterials
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تاريخ الإنعقاد:
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12 -14 September 2016
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مكان
الإنعقاد:
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Surrey,
UK
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طبيعة المشاركة:
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Poster
Presentation
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عنوان المشاركة:
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Determining
the number of sheets in few-layer graphene using nanoscale two-probe
microscopy
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ملخص المشاركة:
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Recently, graphene has received a
remarkable amount of interest due to its extraordinary electrical,mechanical and electrochemical properties
which makes it a promising candidate for different applications such as
switches, mass sensing and energy storage1-3 While single layer graphene has
received a lot of attention, the behavior of few-layer graphene (FLG) may
offer more attractive properties for practical device fabrication. For
example, FLG offers a better transparent conductive electrode as a result of
the lower resistance4. In addition, the inplane thermal conductivity in FLG
is less affected by substrate and impurity effects5 and it can be used as a
heat insulator as the cross-plane thermal conductivity is more than two
orders of magnitude higher than inplane6. Although different methods have
been used to fabricate graphene such as chemical vapor deposition, mechanical
exfoliation of graphite stays as an ideal method to produce and explore
pristine graphene. Since the properties of graphene modify with the thickness
of graphene, it is important to determine the number of graphene layers in
the film accurately7. The lack of a reliable method to determine the number
of sheets in FLG may be the reason of limitation studies of FLG7. This study
shows that an Omicron multi-probe system can be used to determine the number
of layers in FLG precisely.
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المؤتمر (4):
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عنوان المؤتمر:
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AEM2016:
8th International conference on Advanced Nanomaterials
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تاريخ الإنعقاد:
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12 -14 September 2016
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مكان
الإنعقاد:
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Surrey,
UK
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طبيعة المشاركة:
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Poster
Presentation
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عنوان المشاركة:
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Manipulation
and displacement measurements of graphene ripples using multi-probe
microscopy
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ملخص المشاركة:
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Graphene is a promising 2D material for
many applications due to its outstanding thermal, electronic and mechanical
properties1-3. This thin 2D material naturally holds nano-ripples when
suspended4. Also, extrinsic rippling can be imparted to graphene when is
deposited on a substrate that varies from its intrinsic rippling due to the
graphene-substrate interaction5. Since this affects the electronic and
mechanical properties of graphene, the rippling deformation must be
controlled. This study displays the manipulation and measurement of
nanoripples of suspended graphene sheets, as well as layers of the same
sheets sitting on the substrate using multi-probe microscopy.
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