SURFACE-ENHANCEMENT OF FIBER PROBES FOR BIOSENSOR
As this is a broad project where different approaches are suggested, it will be possible for several master
students to apply.
Background
Spectroscopy for qualitative and quantitative sensing is a rapidly expanding area of sensing that employs
optical methods. Spectroscopy has traditionally been used for gas sensing and other industrial uses, and is now
extending into other fields such as sensing applications in medicine.
Raman spectroscopy is a method that employs Raman scattering in order to detect specific compounds. Raman
scattering occurs due to vibrational and rotational modes in a molecule, and provides a fingerprint which can
be used to identify specific molecules and quantitatively measure them.
The major limitation of Raman spectroscopy is the small scattering cross-section, which gives a very small
signal strength. Many variants of Raman spectroscopy have been developed in order to enhance the response
and increase the usefulness of the method. For example, the Raman scattering signal can be increased by
surface-enhanced Raman scattering (SERS), due to excitation of localized surface plasmon resonances
(LSPRs) of nanostructured metal surfaces. LSPRs are a resonant oscillation of conduction electrons in the
nanostructures or nanoparticles, which occur when the frequency of the photons from the laser matches the
oscillation frequency of the surface electrons. This leads to a magnification of the incident light, which gives
a direct increase in the amount of Raman scattering. The Raman-scattered light is then further amplified by the
LSPRs.
Research in Raman spectroscopy for biological measurements is a quite new activity at the Department of
Electronic Systems. Both theoretical and experimental work are being explored. Several Phds and a Postdoc
are developing a set-up for Raman spectroscopy.
The project will be integrated with the Digital Life Norway, Double Intraperitoneal Artificial Pancreas project
funded by the Research Council of Norway (2016-2020). See http://ww.ntnu.ed/web/dln/research-projects .
Goals
The aim of this project is to design and optimise the surface-enhancement of a fiber probe used for Raman
spectroscopy of biological fluids. Surface enhancement can be achieved by coating the fiber probe with gold
or silver nanoparticles. The coating process can be performed at the NTNU Nanolab, and testing of the fiber
probe will be done at the Electronic Systems Department. If there is interest, it will also be possible to
numerically simulate the structures, for example with COMSOL Multiphysics.
Part of the project will be to perform a literature study on the state-of-the-art SERS systems. Techniques for
surface-enhancement will be studied in particular. In order to attach the nanoparticles to the fiber probe, the
surface will have to be prepared with a chosen method. Both the surface preparation method and the type of
nanoparticles used can be investigated during this project. Two main experimental methods are suggested for
optimising the surface-enhancement.
Method 1:
The surface of the probe can be prepared through silanization, which covers the surface in a type of functional
molecule. Nanoparticles can then be deposited in a semi-monolayer by dipping the fiber in a solution
containing the nanoparticles. The quality of the surface-enhancement will depend on the size and geometry of
the nanoparticles.
Prosjekt-/masteroppgaver om elektromagnetiske
metamaterialer
Metamaterialer er kunstige, periodiske strukturer der gitterkonstanten er mye mindre
enn en bølgelengde. Dermed vil materialet ideelt se ut som et homogent medium, med
en effektiv permeabilitet og permittivitet. Man kan oppnå permeabiliteter og
permittiviteter som ikke finnes i naturlige materialer. F.eks. har det blitt demonstrert
negative parametre, som igjen gir negativ brytningsindeks. Slike materialer kan
brukes til å lage perfekte linser (som kan oppløse detaljer mindre enn en bølgelengde).
Man kan også lage mer kompliserte, anisotrope materialer som kan implementere en
vilkårlig transformasjon av det elektromagnetiske feltet, slik som den som trengs for å
få til en usynlighetskappe.
Fordi gitterkonstanten må være mye mindre enn en bølgelengde, er det lettest å lage
metamaterialer for bruk innen radio- og mikrobølgeteknologi. Det er en rekke
interessante anvendelser her, f.eks. effektive, miniatyriserte antenner. Etter hvert som
man kan strukturere materialene på nanonivå, kan metamaterialene å få stor betydning
innen fotonikk/optikk.
Oppgave: Numerisk homogenisering av metamaterialer
Når man skal designe metamaterialer og/eller forstå egenskapene deres, trengs det
algoritmer for å beregne den effektive permittiviteten og permeabiliteten. Denne
oppgaven går ut på å bruke og videreutvikle en numerisk algoritme på datamaskin for
å beregne disse, til et vilkårlig metamateriale som funksjon av frekvens og bølgetall.
Metoden er en såkalt Plane Wave Expansion Method sammen med gitte metoder for
homogenisering.
Oppgaven vil bestå i først et lite litteraturstudium, deretter analytiske argumenter og
programmering av den numeriske algoritmen. Den kan utføres på Kjeller eller i
Trondheim.
Oppgave: Multipoler i metamaterialer
I praksis vil ikke bare elektriske og magnetiske dipoler, men også kvadrupoler ha
betydning i metamaterialer. Faktisk så viser det seg at elektriske kvadrupoler ofte har
like stor betydning som magnetiske dipoler. Vi ønsker derfor å vurdere hvordan dette
kan utnyttes til nye typer kunstige materialer, hvilket kan vise seg å være nyttig for
anvendelser fra radio-frekvenser til fotonikk. I denne oppgaven skal det derfor
undersøkes hvilken betydning kvadrupolleddet har når man løser Maxwells ligninger i
noen aktuelle situasjoner, slik som f.eks. refleksjon og transmisjon på en grenseflate
(Fresnels ligninger).
Oppgaven vil bestå i først et litteraturstudium, deretter analytiske argumenter og
muligheter for numeriske beregninger. Den kan utføres på Kjeller eller i Trondheim.
Veileder:
Hans Olaf Hågenvik, [email protected].
Faglærer:
Johannes Skaar, tlf. 48497352, [email protected].
Forslag til prosjektoppgaver H2017
Nanoteknologi/elektronikk
Jostein Grepstad
Ved Institutt for elektroniske systemer drives forskning basert på epitaksiell vekst og
nanoskala strukturering av funksjonelle oksid tynnfilmer. Forskningen omfatter nye
dielektrika, ferroelektrika (i.e., piezoelektriske og elektrooptisk aktive materialer),
magnetiske og elektrisk ledende oksider og deres grensesjikt i flerlags strukturer
(herunder funksjonelle oksid multilag, substrat, metallkontakter og maskelag for
strukturering) . Oppgaven nedenfor er tilknyttet denne forskningen, og vil kunne
videreføres i en påfølgende hovedoppgave.
1. Røntgen fotoemisjonsstudier (XPS) av grenseflatekjemi i metallmasker
for fremstilling nanomagnetiske strukturer i (La,Sr)MnO3 tynnfilmer
 1 student
Magnetoelektroniske (spinntronikk) komponenter, så som lesehodet i moderne platelager (hard drives)
og magnetiske hurtigminne (MRAM), hviler i stor grad på multilag av magnetiske tynnfilmer, der et
antiferro-magnetisk lag tjener til å låse magnetiseringen i et tilstøtende ferromagnetisk referansesjikt vha.
en effekt kjent som ”exchange bias” (EB). Ved hjelp av en to-trinns struktureringsteknikk1 har vi påvist2
hvordan doménestruktur og magnetisk svitsjing av nanomagneter, definert vha. elektronstrålelitografi i
epitaksielle tynnfilmer av LaFeO3 og LaFeO3/La0.7Sr0.3MnO3 (LSMO) bilag, påvirkes av magnetenes
geometri, størrelse og orientering relativt filmens krystallakser.
Denne prosjektoppgaven er knyttet til mønstringen av filmene, som skjer ved elektronstrålelitografi i
kombinasjon Ar+ ioneimplantasjon gjennom ei metallmaske. Vi har så langt benyttet Cr som
maskemetall. Nye undersøkelser viser imidlertid av metalliseringen i kombinasjon med påfølgende ets
for stripping av Cr-masken skader filmene og deres magnetiske egenskaper. Dette trenger vi å finne ut
av, og ønsker derfor å gjennomføre en XPS (x-ray photoemission spectroscopy) studie av LSMO-filmer
metallisert med Cr og alternative maskematall (Cu, Au) og deretter strippet. Vi ønsker også å studere
LSMO filmoverflaten før og etter oksygen ”ashing”, som vi har funnet skader de magnetiske egenskaper
til filmen.
Filmene vil bli fremstilt i PLD-laboratoriet ved Institutt for elektroniske systemer (IES), metallisering
vil finne sted i NTNU NanoLab. XPS-målingene vil bli utført i laboratoriet ved IES (administrativt
underlagt NanoLab f.o.m. 2017). Prøvematerialet vil også bli karakterisert med scanning
elektronmikroskopi (SEM), atomær-kraftmikroskopi (AFM) og magnetiske målinger (VSM) i NanoLab
og laboratoriene ved IES.
1
Y.Takamura et al., Nano Lett. 6, 1287 (2006); E. Folven et al., J. Electron Spectroscopy and Related Phenomena 185, 381 (2012)
E. Folven et al., Nano Lett. 10, 4578 (2010); E. Folven et al., Phys. Rev. B 84, 220410(R) (2011); E. Folven et al., Nano Lett. 12,
2386 (2012), Y. Takamura et al., Phys. Rev. Lett. 111, 107201 (2013); E. Folven et al., Phys. Rev. B 92, 094421 (2015); M.S. Lee
et al., ACS Nano, DOI:10.1021/acsnano.6b03770 (2016)
2
Faglærer:
Prof. Jostein Grepstad, rom A471, e-post: [email protected]
(p.t. ved Paul-Drude-Institut für Festkörperelekttronik, Berlin)
Veileder:
Ambjørn Dahle Bang, rom A4xx, e-post:
2. Modellering av spinnkopling og magnetisk doménestruktur i tynnfilm
nanomagneter  1 student
Mikro-/nanomagnetisme omhandler magnetiske materialer og komponenter på mesoskopisk skala, dvs.
større enn atomær skala, men med dimensjoner som innebærer at materialets volumegenskaper ikke gir
en representativ beskrivelse av observerte magnetiske fenomen og egenskaper. Mikro-/nanomagnetisk
modellering benyttes for å beskrive både harde og myke magnetiske materialer, flerlags magnetiske
tynnfilmstrukturer, materialer for magnetisk minne og komponenter som lesehoder og magnetiske
sensorer.
Denne prosjektoppgaven går ut på simulering av doménestruktur og magnetisk svitsjing for
nanomagneter av forskjellig størrelse og geometri, til støtte for eksperimentelle studier av magnetiske
tynnfilm nano-strukturer i vår ”Oxide Electronics Group” ved Institutt for elektronikk og
telekommunikasjon.2-6 Arbeidet vil være basert på bruk av åpen programvare kjent under akronymet
OOMMF (The Object Oriented Micro-Magnetic Framework).1 Oppgaven vil egne seg for en student
med interesse for modellering.
1
http://www.ctcms.nist.gov/~rdm/mumag.org.html,
http://math.nist.gov/~MDonahue/micromag.html
2
E. Folven et al., Nano Lett. 10, 4578 (2010)
E. Folven et al., Phys. Rev. B 84, 220410(R) (2011)
E. Folven et al., Nano Lett. 12, 2386 (2012)
5
E. Folven et al., J. Electron Spectroscopy and Related Phenomena 185, 381 (2012)
6
Y. Takamura et al., Phys. Rev. Lett. 111, 107201 (2013)
3
4
Faglærer:
Prof. Jostein Grepstad, rom A471, e-post: [email protected]
Veileder:
Dr. Erik Folven, rom A481, e-post: [email protected]
Master thesis suggestion
Relevant for: Physics/Chemistry/Materials science/Nanotechnology
Synthesis and/or device modeling of organic silicon hybrid solar cells
Organic-Si hybrid solar cells are one of the emerging photovoltaic (PV)
technologies. Efficiencies in excess of 20% have already been reported recently, and
this high efficiency has been achieved only within the past few years. The cells are
composed of an n-type Si wafer and an organic polymer called poly(3,4ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) used as the emitter,
with p-type electrical conductivity. This type of solar cell provides a unique possibility
to combine the high energy conversion efficiency of crystalline Si solar cells with the
potentially low fabrication cost of organic solar cells. The goal of this project is a
theoretical and/or experimental study of organic/Si hybrid cells.
The experimental part of the project will be deposition of commercially
available PEDOT:PSS on n-Si wafers usingthe spin coating and characterization of
optical and electrical properties of this structure. Si surface passivation will be studied
by functionalizing PEDOT:PSS with different types of inorganic nanoparticles, such
as, e.g., Si, produced in the IFE Department for Solar Energy. Finally, Si/organic
heterojunction solar cells will be fabricated and characterized.
The theoretical part consists of device modeling of two different solar cell
designs, with the polymer emitter layer placed in the front side or back side of the cells.
Optimal solar cell parameters and ultimate device performance will be estimated. The
software to be used is Silvaco Atlas, for which IFE has the necessary competence and
software license.
The work will be performed at the IFE Department for Solar Energy and at
NTNU. Well-developed infrastructure and experienced supervisors and lab engineers
will be available for both the experimental and theoretical work. No prior knowledge
of using the Silvaco Atlas or the experimental techniques is necessary.
IFE is located at Kjeller, ~20 km east of the center of Oslo. The solar energy
group usually trains multiple master students from the universities at any given time,
and the laboratory is relatively new with state-of-the-art equipment and offices.
Welcome to IFE!
Contacts:
Erik S. Marstein
Director of the FME Centre
“Solar United”
Department for Solar Energy,
IFE
Mobile: (+47) 9011 7762
E-mail:
[email protected]
S. Zh. Karazhanov and
Halvard Haug
Department for Solar Energy,
IFE
E-mail: [email protected]
E-mail: [email protected]
Jostein Grepstad
Professor,
Department of Electronic
Systems
Tel: +47 73592721
Tel: +47 47418251
E-mail:
[email protected]
1. Magnetisk mikroskopi på nanostrukturer for bruk i spinn-logikk
 1 student
Digital elektronikk som baserer seg på vekselvirkende magnetiske spinn fremfor transport av elektrisk
ladning vil ha mange av de karakteristika som er ønskelige i neste generasjons applikasjoner for digital
logikk. Ved å flippe spinn i stedet for å flytte ladning kan de ohmske tapene som er uunngåelige i
konvensjonell elektronikk elimineres og med dette den primære kilden for spillvarme i mikrochips
fjernes. Nanomagnetisk logikk (NML) er et paradigme innen elektronisk databehandling som baserer seg
på propagasjon og prosessering av digital informasjon i nettverk av vekselvirkende nanomagneter [1].
NML er en sterk kandidat for ultra-lavenergi databehandling og kan kombinert med f.eks. multiferroisk
initialisering gi en effektreduksjon på opptil tre størrelsesordener sammenliknet med dagens CMOS
teknologi [2].
Vi har gjennom flere år studert hvordan doménestruktur i nanomagneter kan kontrolleres via geometri,
størrelse, orientering og magnetisk kopling over grenseflater [3-6]. Denne prosjektoppgaven bygger
videre på dette arbeidet og vil primært omfatte bruk av et nytt lavtemperatur MFM (magnetic force
microscope) ved Institutt for elektroniske systemer (IES). Dette for å undersøke nanomagneter til mulig
bruk i NML. Filmene vil bli fremstilt i PLD-laboratoriet ved IES, mens struktureringen vil bli utført i
NTNU NanoLab. De nanostrukturerte prøvene vil bli karakterisert med sveipelektronmikroskopi (SEM)
og atomærkraftmikroskopi (AFM) forut for de magnetiske målingene.
1
A. Imre et al., Science 311, 205 (2006)
M. S. Fashami et al., Nanotechnology 23, 105201 (2012)
E. Folven et al., Nano Lett. 10, 4578 (2010)
4
E. Folven et al., Nano Lett. 12, 2386 (2012)
5
Y. Takamura et al., Phys. Rev. Lett. 111, 107201 (2013)
6
E. Folven, et al. Phys. Rev. B 92, 094421 (2015)
2
3
Faglærere:
Førsteamanuensis Erik Folven, rom A-467, e-post: [email protected]
Prof. Jostein Grepstad, rom A471, e-post: [email protected]
Veileder:
Ambjørn Dahle Bang, rom A-461, e-post: [email protected]
SILICON NANOPHOTONIC BIOSENSOR
Introduction
Photonics is currently one of the most rapidly developing branches of
science that explores the properties of light for solving various problems.
The list of applications is extensive and the impact it has on our lives is
often compared to that of what electronics has achieved since the invention
of a transistor. Information processing, ultrafast telecommunication, medical
diagnosis, optical displays of various kinds, ultrahigh-precision sensors are
only few examples where photonics has become prominent. With
continuously expanding ranges of new applications and materials, this
branch of research is believed to transform our societies in the next few
decades.
Silicon as platform for photonic devices is interesting due to its high
light confinement, and because standard lithography and CMOS
processes can be used to fabricate micro - and nanoscale
components. Because silicon is CMOS compatible, i ntegrated systems
on a single semiconductor chip can be realized. Examples of micro- and
nanophotonic components are dielectric waveguides, microresonators of
various types, light modulators, couplers, periodic structures and more.
Especially, a certain type of periodic structures, known as photonic crystals,
due to their extraordinary ability of light confinement, possess a truly
remarkable potential for applications in both fundamental research and
industry.
Research in silicon photonics is an ongoing activity at the Department of
Electronic Systems. Both theoretical and experimental work is explored. A
number of master students and PhD students have been/are designing and
processing silicon-based photonic crystal and waveguide structures.
Processes and recipes have been developed at the NTNU Nanolab to
fabricate these silicon-based structures. Optimization is an ongoing task.
The project will be integrated with the Digital Life Norway, Lab-on-a-chip
biophotonic sensor platform for diagnostics project funded by the Research
Council of Norway (2016-2020). See http://www.ntnu.edu/web/dln/researchprojects .
Goals
The aim of this project is to design and simulate a silicon nanophotonic
biosensor. To achieve high sensitivity it is likely that the sensor will
be ring resonator based or interferometric (e.g. based on a Mach Zehnder configuration). Both waveguide and photonic crystal
structures can be pursued. The component can be processed at the
NTNU Nanolab as part of the master’s project, or the student can
continue to optimize simulations.
Part of the project will be to perform a literature study on the stateof-the-art silicon photonic sensors. In particular surface
functionalized biosensors will be studied. To make the sensor
specific to a target biomolecule, the surface is coated with
antibodies via chemically activated funct ional groups. These surface
coated antibodies act as specific capture agents and protein binding
to these surface receptors induces a sensor response. The antigen antibody binding causes a surface refractive index change of the
functionalized sensor and the concentration of the binding antigens
can be measured.
In parallel with the literature study the student will learn the basics of
the simulation software. The main goal of the project will be to design the
photonic sensor by the aid of numerical simulations using COMSOL
Multiphysics, which is based on Finite Element Method (FEM). Other
simulation tools may also be utilized such as, MIT Photonic Bandgaps
(MPB) to calculate eigenmodes and MIT Electromagnetic Equation
Propagation (MEEP), which is finite-difference time-domain (FDTD) based.
If time allows during the Fall semester, cleanroom courses will be taken at the Nanolab to
qualify the student to fabricate the device in the NTNU Nanolab. It is also possible to take
these courses at the beginning of the master’s project.
Figure 1: Examples of structures simulated using FEM, COMSOL
Multiphysics.
Supervisors
Astrid Aksnes, Prof., room B413, [email protected] , tel. 73597699
Jens Høvik, PhD student, room B412, [email protected]
Student/master projects in nano-optoelectronics
2017/18 http://www.iet.ntnu.no/~weman/
The nano-optoelectronics group at the Department of Electronic Systems
(IES) focuses on growth, characterization and processing of III-V semiconductors
for use in photonics, solar cell technology and sensor applications. A strong focus
is being made on III-V semiconductor nanowires (NWs) grown by molecular
beam epitaxy (MBE lab). Fabrication of NW devices is being explored by electron
beam lithography as well as by nanoimprint and focused ion beam techniques
using NTNU NanoLab. Optoelectronic characterization of individual nanosystems
using techniques such as low temperature photocurrent and electroluminescence
(Nanophotonics lab) is done in order to understand, improve and utilize quantum
size effects for future nanophotonic device applications. In collaboration with
Prof. Ton van Helvoort at IFY we also perform detailed structural characterization
of the nanowires using the TEM Gemini Center. Some of the projects suggested
will be performed in collaboration with our spin-off company CrayoNano AS.
Normally you will work in close collaboration with a postdoc or a PhD
student of the group to achieve your goals in the project. The projects normally
have an applied character and can be both theoretical and practical, and some
include clean room work in NTNU NanoLab. The projects are most suited for
students from the “nano-electronics” and “nanomaterials” branch of the
Nanotechnology program and the “nano-electronics and photonics” branch of the
Electronics program, but other students with a strong background in these fields
are also welcome.
Faculty supervisors for the projects are:
Prof. Helge Weman, [email protected], Room B415 in Electro.
Prof. Bjørn-Ove Fimland, [email protected], Room A381 in Electro.
Some recent publications from our group:
1. A.M. Munshi, D.L. Dheeraj, V.T. Fauske, D.C. Kim, A.T.J. van Helvoort, B.O. Fimland, and
H. Weman, Nano Lett. 12, 4570 (2012).
2. L. Ahtapodov, J. Todorovic, P. Olk, T. Mjåland, P. Slåttnes, D.L. Dheeraj, A.T.J. van Helvoort,
B.O. Fimland, and H. Weman, Nano Lett. 12, 6090 (2012).
3. D.C. Kim, D.L. Dheeraj, B.O. Fimland, and H. Weman, Appl. Phys. Lett. 102, 142107 (2013).
4. A. M. Munshi, D. L. Dheeraj, V. T. Fauske, D. C. Kim, J. Huh, J. F. Reinertsen, L. Ahtapodov,
K. D. Lee, B. Heidari, A. T. J. van Helvoort, B. O. Fimland, and H. Weman, Nano Letters, 14,
960 (2014).
5. G. Signorello, E. Lörtscher, P.A. Khomyakov, S. Karg, D.L. Dheeraj, B. Gotsmann, H. Weman
and H. Riel, Nature Communications, 5, 3655 (2014).
6. J. Huh, H. Yun, D.C. Kim, A.M. Munshi, D. L. Dheeraj, H. Kauko, A.T.J. van Helvoort, S.W.
Lee, B.O. Fimland, and H. Weman, Nano Letters, 15, 3729 (2015).
1.
Fabrication and characterization of vertical III-V semiconductor
nanowire/graphene junction devices (involves work in NanoLab)
In vertical III-V semiconductor NW/graphene devices where NWs are grown
directly on graphene substrates there are many technical and scientific challenges
still not fully understood. One of them is how the ohmic contact is formed and
works between the NWs and graphene. In this project, the student will focus on
the fabrication processes for vertical NW/graphene junction devices. The whole
fabrication process from the graphene substrate preparation to the final
metallization on top of the NW array will be carried out by using various facilities
in NanoLab, in close collaboration with other members in the nanooptoelectronics group in IES and CrayoNano AS. If the process development is
successful and time allows, the optoelectronic properties of vertical NW/graphene
junction devices will be further investigated.
Supervisors:
Ph.D. student: Ida-Marie Høiaas, [email protected]
Adjunct associate professor: Dong Chul Kim, [email protected]
2. Process development and characterization of graphene-Si junction devices
(involves work in NanoLab)
In the field of graphene research, more and more efforts are focused towards
integrating graphene with existing technologies and developing actual devices. In
our group we have developed a method for depositing large-grained crystalline Si
on graphene via a metalinduced crystallization process. The next steps in this work
are to investigate the quality of the synthesized materials and the electronic
properties of the graphene/Si heterostructure by making an actual device. The
project will involve clean room work as well as device characterization.
Furthermore, process optimization of the Si deposition on graphene and its doping
will be performed in parallel with the device development. As such, the project
combines in-depth understanding of the structural and functional properties of
semiconductor nanomaterials.
Supervisors:
Ph.D student: Ida-Marie Høiaas, [email protected]
Adjunct associate professor: Dong Chul Kim, [email protected]
3. Fabrication and characterization of single III-V semiconductor nanowire
devices (involves work in NanoLab)
Our group has a long history in developing III-V semiconductor nanowire devices
ranging from GaAs-based nanowire (NW) array solar cells to GaN-based NW
array LEDs. In order to realize such NW array devices it is very important to
understand the optoelectrical properties of each single NW. Through this project,
the student will have a great opportunity to participate in the fabrication and
characterization of single NW devices. She/he will start to learn various
fabrication processes including e-beam lithography (EBL) in NanoLab, and finally
carry out opto-electrical measurements of the devices at Nanophotonics lab in IES.
Supervisors:
Ph.D student: Anjan Mukherjee, [email protected]
Adjunct associate professor: Dong Chul Kim, [email protected]
4. Fabrication and characterization of embedded nanowire/graphene hybrid
devices for gating structure. (involves work in Nanolab)
GaAs is one of the most important III-V semiconductor NW structure with a high
potential for high-efficiency solar cells and photo detectors. In addition, using
graphene as a highly conducting and transparent electrode could lead to enhanced
absorption efficiency of single GaAs NW optoelectronic devices as well as enable
basic NW contact studies through a Fermi level tuning of the graphene. The key
challenge to make a NW/ graphene hybrid devices NW on a flat surfaced structure
for successful graphene transfer, has recently been demonstrated by our group.
The fabrication of graphene/dielectric/graphene structure (gating structure) on an
embedded nanowire configuration is yet to be solved. In this project, the student
will study the fabrication process to make a gating structure of graphene on top of
an embedded NW and perform optoelectrical measurements. The whole process
from substrate preparation to final metallization through several electron beam
lithography (EBL) steps will be carried out by using various facilities in Nanolab.
Supervisors:
Ph.D student: Anjan Mukherjee, [email protected]
Adjunct associate professor: Dong Chul Kim, [email protected]
5. Wafer-scale hole array patterning on graphene substrates for the selective
area growth of semiconductor nanowires
(involves work in NanoLab)
The recent demonstration of successful growth of III-V nanowires (NWs) on
graphene is an important cornerstone in next generation high functional III-V
semiconductor optoelectronic devices where flexible, conducting, and extremely
light, single carbon layer graphene is used as a substrate. Together with process
engineers in CrayoNano AS, the student will develop a highly reproducible and
fast way to make sub-100 nm hole patterning on graphene wafers with an oxide
mask for selective area growth of NWs in a well-ordered array form. EBL is
primarily used to make the hole patterning with various process parameter
optimizations. Other nanolithography techniques such as colloidal lithography will
be also investigated and developed as a cheap alternative for EBL.
Supervisors:
CrayoNano AS engineer: Carl Philip Heimdal,
[email protected]
Leidulv Vigen, [email protected]
Adjunct associate professor: Dong Chul Kim, [email protected]
6. InGaN nanowires for water-splitting applications
(involves work in NanoLab)
Solar-fuel conversion is desirable for high-efficiency green energy production, and
the solar water splitting for hydrogen generation can be a potential source of
renewable energy for fuel cells used in mobile vehicles etc.. In this project, the
student will use the newly installed molecular beam epitaxy (MBE) system
equipped with a nitrogen plasma source to grow the GaN/InGaN nanowires, which
will be used for the photocatalytic water splitting. The student will aid in growing
the GaN/InGaN nanowires, and be involved in analyzing the cell performance
with a variety of catalysts, such as Pt, rhodium (Rh)/chromium-oxide (Cr2O3)
core–shell nanoparticles etc.. In addition, the student will use the high-resolution
scanning electron microscopy (SEM) facility with energy dispersive x-ray (EDX)
elemental analysis in NTNU Nanolab to characterize the nanowire compositions.
Supervisor:
Postdoc: Dingding Ren, [email protected]
7. Growth study of AlGaN nanowires on graphene for UV LED applications
(involves work in NanoLab)
GaN and its alloys (InGaN and AlGaN) have become one of the most important
materials in the semiconductor industry, particularly for light emitting
applications. Compared to InGaN, which has been well-exploited for visible
LEDs, the development of AlGaN based UV LEDs is much more challenging.
Such LEDs are in high demand for UV light based sterilization and disinfection.
The utilization of nanowire structures significantly enhance the crystal quality of
the active AlGaN material, with no dependence on the crystalline nature of
underlying substrate, not achievable using conventional thin film structures.
Graphene will be used as an epitaxial substrate for the AlGaN nanowire growth
and transparent electrode. Combined such AlGaN nanowire/graphene structure
could be a key factor in advancing the progress of future UV LEDs.
The student will start the project with a nucleation study of GaN and further
AlGaN nanowires grown by molecular beam epitaxy on graphene. Different
characterization techniques (SEM, XRD, Raman, PL and electrical
characterization) will be employed in order to optimize the structural and electrical
properties of the grown AlGaN nanowires. Fully processed UV LED structures
can be fabricated and studied a s the part of a master thesis project in the spring
2018.
Supervisors:
PhD student Andreas Liudi Mulyo, [email protected]
PhD student Anjan Mukherjee, [email protected]
8. Time-resolved spectroscopy and optical pumping of GaAsSb nanowire
laser arrays
Semiconductor nanowires (NW) have been successfully applied for optoelectronic
devices such as lasers and light emitting diodes. GaAs NWs with multiple axial
GaAs/GaAsSb heterostructured superlattice inserts have been fabricated at the
Nanowire group at NTNU and found to be lasing in the near infrared spectral
region. However, all experiments conducted so far have been on single NWs,
detached from the growth substrate. The next step towards achieving a NW-based
laser device is to study as-grown NW laser arrays with in-plane optical excitation
and head-on collection of the luminescence signal. The student will work at the
Nanophotonics lab at NTNU on developing an optical setup that will enable
conducting this experiment. The project involves working with Class 4 lasers and
cryogenic liquids (i.e. liquid He), and has a strong focus on nanophotonics and
solid state physics.
Supervisor:
Postdoc: Lyubomir Ahtapodov, [email protected]
Postdoc: Dingding Ren, [email protected]
9. Correlated micro-photoluminescence and transmission electron
microscopy of GaN/InGaN nanowires.
GaN/InGaN nanowires (NW) hold great potential for fabricating NW-based light
emitting diodes for future micro-display applications (wearables, VR, AR etc.). In
this project, the student will conduct micro-photoluminescence spectroscopy (µPL) on single GaN/InGaN NWs, deposited on transmission electron microscopy
(TEM) substrates in order to allow for post-PL structural characterization of the
same single NWs. In the course of the project, an optical setup, which allows for
excitation with UV light (i.e. below 300 nm) will be developed. The student will
mainly work in the Nanophotonics lab at NTNU, however there will be a close
collaboration with the staff at the MBE lab and the TEM facilities at IFY. The
project involves using a Class 4 pulsed fs Ti:Saphire laser and a frequency
doubler/tripler unit in order to achieve UV excitation of the samples. The project
has a strong focus on optics and spectroscopy of advanced nanomaterials.
Supervisor:
Postdoc: Lyubomir Ahtapodov, [email protected]
Postdoc: Dingding Ren, [email protected]
Method 2:
Surface-enhancement by film deposition over nanospheres can also be achieved. In this method one layer of
polymer nanospheres is attached to the fiber tip, which is then coated with a thin Ag film (~200 nm) using
thermal deposition. Alternatively, by coating microspheres with a gold layer and sonication of the fiber probe,
spheres are removed leaving an array of gold triangular islands.
Figure 1: Suggested set-up for sensing with the fiber probe (top), enlarged scheme of the sensing mechanism
in the probe tip (middle), and an example of a tapered fiber (bottom).
Supervisors
Astrid Aksnes, Prof., room B413, [email protected] , tel. 73597699
Karolina Milenko, Postdoc, room B419, [email protected]
Ine Jernelv, PhD student, room B419, [email protected]