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Energy (2017) 000–000 131–138 EnergyProcedia Procedia119 00 (2017) www.elsevier.com/locate/procedia
International Conference on Technologies and Materials for Renewable Energy, Environment and International Conference on Technologies and21-24 Materials Renewable Energy, Environment and Sustainability, TMREES17, Aprilfor 2017, Beirut Lebanon Sustainability, TMREES17, 21-24 April 2017, Beirut Lebanon
Contacting of Si/SiO2 core/shell nanowires using laser The 15th International on District Heating using and Cooling Contacting of Si/SiOSymposium nanowires laser 2 core/shell photolithography photolithography Assessing the 1,3 feasibility1,2,*of using the heat demand-outdoor F.Benyettou1,3, A.Aissat1,2,*,M.E.A. Benamar33, I.Berbezier22 F.Benyettou , A.Aissat ,M.E.A. Benamar temperature function for a long-term district, I.Berbezier heat demand forecast Laboratory LATSI Faculty of Technology University of Blida.1, 09000 Blida, Algeria 1
Laboratory LATSI FacultyAix-Marseille of TechnologyUniversity University13397Marseille of Blida.1, 09000 Blida, IM2NP-CNRS(UMR7334), Cedex 20,Algeria France
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a b c c IM2NP-CNRS(UMR7334), Aix-Marseille 13397Marseille Cedex 20, Algeria France, O. Le Corre I. Andrića,b,c *, A.FUNDAPL Pinaa, P. Ferrão , University J.University Fournier ., B.09000 Lacarrière Laboratory Faculty of Science of Blida.1, Blida, 23
3 Laboratory FUNDAPL Faculty of Science University of Blida.1, 09000 Blida, Algeria IN+ Center for Innovation, Technology and Policy Research - Instituto Superior Técnico, Av. Rovisco Pais 1, 1049-001 Lisbon, Portugal b Veolia Recherche & Innovation, 291 Avenue Dreyfous Daniel, 78520 Limay, France Abstract c Département Systèmes Énergétiques et Environnement - IMT Atlantique, 4 rue Alfred Kastler, 44300 Nantes, France Abstract a
The contamination results of extended ion or electron beam irradiation, the type of substrate used, the time required The contamination of extended or electron beam irradiation, the type of substrate used, the limitations time required to contact a set of results nanowires to gain ion accurate acknowledge on nanowires properties are the main of to contact abeam set of(FIB) nanowires to gain accurate acknowledge on nanowires properties characterization. are the main limitations of focused ion and electron beam lithography (EBL) techniques for nanowires We present Abstract focused ion beam (FIB) writing and electron beam which lithography (EBL) techniques for nanowires We Si/SiO present2 in this latter, a direct technique is laser photolithography to contact characterization. a set of core/shell in this latter, a directbywriting which laser photolithography to LMAIS-FIB contact a setusing of core/shell metalisalloy source focused ion beam Au+ ions toSi/SiO allow2 nanowires fabricated 30 KeVtechnique AuSi liquid District heating networks areKeV commonly in alloy the literature as oneion of beam the most effective solutions + decreasing the liquid metal source focused LMAIS-FIB using Aufor ions to allow nanowires fabricated by 30 AuSiofaddressed forward the electrical characterization these nanowires. greenhouse gas emissions from the building sector.nanowires. These systems require high investments which are returned through the heat forward the electrical characterization of these
sales. Due to the changed climate conditions and building renovation policies, heat demand in the future could decrease, © 2017 Authors. Published Published by by Elsevier Elsevier Ltd. Ltd. ©prolonging 2017 The The Authors. the investment return period. © 2017 The Authors. Published by Elsevier Ltd. Peer-review under responsibility of the Euro-Mediterranean Institute for Sustainable Development (EUMISD). Peer-review under responsibility of the Euro-Mediterranean Institute for Sustainable Development (EUMISD). The main scope this paper is of to the assess the feasibility of using the for heatSustainable demand – Development outdoor temperature function for heat demand Peer-review underofresponsibility Euro-Mediterranean Institute (EUMISD). forecast. The district of Alvalade, located in Lisbon (Portugal), was used as a case study. The district is consisted of 665 Keywords: Nanowires, Laser, photolithography, solar cell. buildingsNanowires, that vary Laser, in both construction period and typology. Three weather scenarios (low, medium, high) and three district Keywords: photolithography, solar cell. renovation scenarios were developed (shallow, intermediate, deep). To estimate the error, obtained heat demand values were compared with results from a dynamic heat demand model, previously developed and validated by the authors. 1.The Introduction results showed that when only weather change is considered, the margin of error could be acceptable for some applications 1. Introduction (the error in annual demand was lower than 20% for all weather scenarios considered). However, after introducing renovation Silicon nanowires Si (NWs) structures with aand length greaterscenarios (some micrometers) than the scenarios, the error value increasedare up one-dimensional to 59.5% (depending on the weather renovation combination considered). Silicon nanowires Si (NWs) are one-dimensional structures with a length greater (some micrometers) than the other sizes (some nanometers). The large surface/volume ratio is useful to enhance the performances of electronic The value of slope coefficient increased on average within the range of 3.8% up to 8% per decade, that corresponds to the other sizes (some nanometers). The large surface/volume ratio is useful to enhance the performances of electronic nanodevices. Recently, Si NWs are widely used in the next generation of CMOS nanodevices like field effect decrease in the number of heating hours of 22-139h during the heating season (depending on the combination of weather and nanodevices. Recently, Si NWsless arethe widely used in the next generation nanodevices like fieldvolume effect renovation(FETS) scenarios considered). On other hand, function intercept increased forCMOS 7.8-12.7% per decade (depending on the transistors [1], junction transistors (JLTs) [2] and tunnel effect of transistors (TETs) [3]. The little transistors (FETS) less for transistors and tunnel effect transistors (TETs) [3]. little cells, volume scenarios). Thejunction valueschoice suggested could be(JLTs) used to[2]modify the[4,5]. function parameters for theofscenarios and ofcoupled NWs makes it a [1], favorable chemical and bio-sensing Another application NWsThe is considered, solar in of NWsthese makes it a favorable choice for chemical and bio-sensing [4,5].and Another application of NWs is solar cells, in improve the configurations accuracy of heat allow demand which toestimations. maximize solar spectrum trapping then increase absorption.
which these configurations allow to maximize solar spectrum trapping and then increase absorption. © 2017 The Authors. Published by Elsevier Ltd.
* Peer-review Correspondingunder author. A. Aissat Tel.:+21325433850; responsibility of the Scientificfax:+21325433850. Committee of The 15th International Symposium on District Heating and address:
[email protected] *E-mail Corresponding author. A. Aissat Tel.:+21325433850; fax:+21325433850. Cooling. E-mail address:
[email protected] 1876-6102© 2017 demand; The Authors. Published by change Elsevier Ltd. Keywords: Heat Forecast; Climate 1876-6102© 2017 The Authors. Published by Elsevier Ltd. Institute for Sustainable Development (EUMISD). Peer-review under responsibility ofthe Euro-Mediterranean Peer-review under responsibility ofthe Euro-Mediterranean Institute for Sustainable Development (EUMISD).
1876-6102 © 2017 The Authors. Published by Elsevier Ltd. Peer-review under responsibility of the Scientific Committee of The 15th International Symposium on District Heating and Cooling.
1876-6102 © 2017 The Authors. Published by Elsevier Ltd. Peer-review under responsibility of the Euro-Mediterranean Institute for Sustainable Development (EUMISD). 10.1016/j.egypro.2017.07.060
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Moreover, they are decreasing the density of states in surface which leads to decrease the recombination of photogenerated carriers and reduce the distance to collecting junction. Usually, two techniques are used for fabrication of NWs: top-down and bottom-up techniques. The top-down technique uses lithography to define the fabricated structure and then transfer it to the substrate by etching or similar way. In bottom-up approach, the material is added to substrate in self-organized way. Bottom-up uses vapor liquid solid (VLS) method for synthesis the NWs, in this method a metallic nanoparticules are employed to growth the NWs [6]. Recently, FIB/ scanning electron microscopy (SEM) dual beam system is widely used for micro and nanofabrication in machining applications [7]. The main element of FIB is called LMIS that generates the ion beam. The advantage of LMIS-FIB is direct local writing and milling shapes with ultimate sizes due to maskless compared to other techniques such as optical lithography and EBL [8]. Most of LMIS used in laboratories and industry operates with Gallium Ga+ ions source [9], this type of LMIS gives good resolution and stability thanks of its low melting temperature and volatility [9]. However, it has several drawbacks and adverse effects on surface of the target material (contamination, heavy implementation ......... etc). Liquid Metal Alloy Ion Source (LMAIS) AuSi and AuGe are appearing as alternative sources for lithography to exceed the Ga LMIS limits [10]. Many techniques have been employed for the electrical characterization of NWs such as EBL and FIB. Although each has limitations, such as; the nature of the substrate used, the time required to connect a number of NWs and also the difficulty of locating a single NWs, especially the NWs grown by VLS technique. Laser photolithography is a powerful technique for contacting and characterizing a set of NWs and it is a good candidate to replace EBL [11] and FIB [12]. Their advantages are that is quick, flexible, maskless, direct writing and contacting patterns on arbitrary substrate; and also can avoid any potential contamination associated with extended ion beam or electron beam irradiation. In addition, the clear visibility of NWs through the photoresist. In this work, we report fabrication of SiO2/Si nanowires on silicon on insulator (SOI) substrate with a width of 450 nm, length of 50 µm and depth of 20 nm using 30 KeV Au+ of AuSi LMAIS-FIB. Laser photolithography is employed for rapid electrical contacting of the NWs using Aluminum metal. Nanostructure NWs FIB SiO2 LMIS VLS FETS JLTs CMOS TETs Ga+ Si LMAIS SOI SEM AFM UV PL EBL RTO
nanowires Focused Ion Beam Silice Liquid Metal Ion Source Vapor Liquid Solid Field Effect Transistors Junction Less Transistors Complementary Metal Oxide Semiconductor Tunnel Effect Transistors Gallium Silicon Liquid Metal Alloy Ion Source Silicon On Insulator Scanning Electron Microscopy Atomic Force Microscopy ultraviolet Photoluminescence Electron Beam Lithography Rapid Thermal Oxydation
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Fig.1. fabrication steps of core/shell Si/SiO2 nanowires.
2. Sample preparation and metallization (100) oriented SOI wafer with a Si layer thickness of about 14 nm is used for nanowires fabrication as shown in Fig.1. The sample is cleaned by the Shiraki method to remove the residual impurities present in the SOI. Before starting the creation of nanowires on our sample using AuSi COBRA FIB/SEM dual beam from Orsay Physics, we made steps of calibration to achieve the optimal parameters of patterning by FIB to be employed on our sample. For this, fours nanopattrening with different parameters as shown in table 1 have been created. Fig.2 represents the integrated SEM images for the fours nanopatterning created by 30 KeV Au+ ions. Atomic force microscopy (AFM) PSIA XE-100 is used for characterization, the analysis of the related AFM images (Fig.3 (a)) allowed us to choose the parameters of the pattern “A” to continue thereafter etching our desired nanowires by FIB. Indeed, in this case the etched depths obtained are consistent with those applied for, and also the AFM profile (Fig.3 (b)) shows that NWs contours and profiles are better defined, with a lower roughness. Using parameters of pattern A, we have fabricated a set of nanowires with a width of 450 nm, length of 50 µm and depth of 20 nm approximately by Au+ ions of AuSi LMAIS-FIB. Next step is to surround the nanowires by thermal oxide SiO2 layer using rapid thermal oxidation (RTO) (Fig.1).
A
B
C
Fig.2. SEM images of the fours nanopatterning created by 30 KeV Au+ for calibration.
D
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Table 1. The important parameters of milling of the fours nanopatterning used for calibration. Parameter/pattern
A
B
C
D
Probe current (pA) Milling depth Z(nm) Milling mode Pattern length (µm) Pattern width (µm)
18.9 20
18.9 20
19 70
19 20
serial 6 0.3
parallel 6 0.3
parallel 6 -
parallel 6 -
0.3
0.3
0.6
0.5
rectangles 2.48
rectangles 2.48
lines 1.29
lines 1.29
Distance between two adjacent patterns (µm) Shapes Time of milling (min)
(a)
A
B
C
D (b)
25 20
Z [nm ]
15 10 5 0
0
2
4
6
8
X[µm] Fig.3. (a) AFM images of the fours nanopatterning created by 30 KeV Au+ for calibration. (b) AFM profile of the nanopattering “A”.
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Large contacts (pads) have been created to connect the nanowires produced. For this, we have used laser photolithography machine. The device employed in the laboratory was Dilase 250 (KLOE Company). The device is equipped a laser diode source emitting at 375 nm, with a power of 70 mW. This equipment offers both vectorial and scanning writing modes and ensures a trajectory within a 100 nm maximum deviation range. Two softwares Kloe Design and Dilase Soft are integrated to allow the patterns design and implementation. The Dilase 250 system is compatible with most of the commercially available photoresists. The advantage of laser photolithography is the direct writing on the sample by scanning patterns under laser beam and therefore does not require a mask as in standard optical lithography [13].This technique is particularly suitable for production of prototypes, where we can realize patterns with a various shapes. The system engraving resolution is ≤ 2 µm. Firstly, we made several resin deposition to produce patterns of different shapes using Dilase Soft as shown in Fig.4 by changing major process parameters (modulation of the laser power and the write speed) until achieving 2 µm of resolution. The type of resin employed was S1805. We have found that a modulation of 10 and write velocity of 11 µm/s are the best parameters which give excellent resolution. Then, we have utilized these optimal parameters to fabricate our pads. The deposition of Al metal has done using lift-off technique.
Fig.4. Top-view optical microscope photograph of lines produced by laser lithography for calibration.
3. Results and discussion The SEM and AFM images of a 20 Si /SiO2 core/shell NWs with a width of 450 nm produced by 30 KeV Au+ LMAIS/FIB are shown in Fig.5 (a) and (b), respectively. It was clear that the NWs produced are well arranged, and their dimensions are effectively checked. Fig.6 (a) exhibits a top-view optical microscope photograph indicating the layout of the resulting Si/SiO2 NWs contacted by two pads of Aluminum Al using laser photolithography. While Fig.6 (b) represents the AFM images of the contacted zone of NWs with Al pads.
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(a)
(b)
(c)
Fig.5. (a) AFM images of 20 Si/SiO2 core/shell NWs with width of 450 nm created by 30 KeV Au+. (b) SEM images of the correspondent NWs. (c) AFM profile
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(a)
(b)
Fig.6. (a) Top view optical microscope of contacted NWs by Al pads (b) AFM images of contacted zone of NWs with Al pads.
4. Conclusion Core/shell Si/SiO2 NWs with width of 450, a length of 50 µm and a depth of 20 nm were produced by 30 KeV Au+ ions of AuSi LMAIS/FIB in this work. These NWs have been contacted by Al pads using laser photolithography. Several experiences have been done in goal to get optimal parameters of milling by FIB and to achieve the best process parameters for laser photolithography. We have found that a modulation of laser power of about 10 and write speed of 11 µm/s give optimal resolution for creation Al pads to contact the NWs by laser photolithography. Finally, we are looking to complete this work by extracting the electrical I-V characteristics and photoluminescence (PL) spectra of the produced NWs for photovoltaic applications.
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lithography for production of
