1、 Silicon Nanowires Synthesized via Microwave-Assisted Chemical Vapor Deposition組員：蔣振龍 王美玲 孫建會 孫瑞瑞 董思寧 殷月偉 第十七組第十七組主要內容Introduction ExperimentExperimental ResultsDiscussionApplication of SiNWsIntroduction of silicon nanowiresnSilicon nanowires have unique electronic and optical properties, it can be

2、wildly used in sensor and electronic industries.nThe synthesis of silicon nanowires are high-cost or high-energy conditions.合成硅納米線的幾種方法合成硅納米線的幾種方法n激光燒蝕：海綿狀的SiNWsn水熱法：（20 nm）n分子束取向附生法(MBE）n金屬催化化學腐蝕方法（單晶性好、軸向可控）nAAO模板法n熱物理蒸發法SiNWs by Laser AblationTEM image of as-grown SiNWs by the thermal physical ev

3、aporation, A new method to synthesis silicon nanowiresnThis is not a new method. Microwave sources have previously been employed in the synthesis of carbon nanotubes. nHowever, to the best of our knowledge, application of a microwave field has not been reported on the growth of SiNWs at ambient cond

4、itions prior to this work. Experiment condition An unmodified 1100 W, 2.45 GHz Emerson domestic microwave oven Trichlorosilane (99%) from Aldrich Substrate materials: （i）14 cm ITO-coated slides from Hartford Glass Co. (surface resistivity15/ ) that were thinned down to 1 mm thickness by mechanical p

5、olishing (substrate A). （ii）1 mm thick ITO-coated glass slides from Aldrich (surface resistivity15/ ) that were cut into rectangles of 14 cm (substrate B). The difference of two substratesSubstrate A:Substrate B:Experimentsubstrates degreased （acetone） Rinse(2-propanol；deionized water)dryDipping（SnO

6、2 colloidal solution ）withdrawn dry thermal treatment(300，3h） microwave reaction vial irradiated (0.5min)testScheme of deposition Scheme 1. Scheme of deposition. HSiCl3(g)+ITO(S)+ wave radiation Si(ads)+ITO(S)+HCl(g)+Cl2(g)Results (SEM)Fig. 1. SEM images of structures obtained on different regions o

7、n a conductive substrate, substrate A: (ab) heated substrate (with an average length of 30 and average diameter of 3 ) (df) heated substrate( average length of30 ) (g-h) unheated substrateResults (SEM)Fig. 2. SEM images of SiNWs (3045 nm diameter) interspersed with Si crystallites (0.3 m diameter) d

8、eposited on conductive ITO surface (substrate B). The various pictures are different magnifications of the same region of the substrate. Results (SEM)Fig. 3. SEM images of porous Si/agglomerated Si nanoparticles observed at edges of deposition area: (a) substrate A and (b) substrate B. Results (EDS

9、analysis)Fig. 4. Representative EDS spectra of the various morphologies observed, (a) EDS spectrum of SiNW bundle, (b) EDS spectrum of Si crystallite and porous matrix, and (c) EDS spectrum of dense Si layer. Results (XPS analysis)Fig. 5. XPS spectrum of SiNW bundles oxygen: 1002 eV (KL1L23), 982 eV

10、 (KL23L23), 536 eV (1S); carbon: 288 eV (1S); silicon: 153 eV (2S), 105 eV (2P1), 101 eV (2P3), 28 eV (2S). ConclusionsSEM analysis of the unmodified substrate A showed a predominantly columnar orientation of its conductive layer, whereas substrate Bs conductive layer was found to be made up of comp

11、act microspheres. Substrates of different ITO microstructure were found to result in Si wires of different morphologies. Chemical analysis showed the structures obtained to be of high purity silicon, comparable to conventional SiNW growth techniques currently in use. DiscussionAdvantages: This metho

12、d is a simple but effective synthesis ofhigh-purity SiNWs using inexpensive equipment. limitations : limited control over the overall structure uniformityand coverage due to the multimode nature of themicrowave field and nonuniform SnO2 nanoparticlesurface coverage. Further studiesFurther studies ar

13、e in progress to improve upon these by:use of a single-mode microwave source for a more uniform electric fielduse of a lower energy precursor, e.g., SiH4, that would increase coverage percentage and achieve even smaller diametersuse of surfactants in nano-SnO2 patterning of the ITO surface for great

14、er dispersion硅納米線在納米電子器件上的應用硅納米線在納米電子器件上的應用n場效應晶體管(FET)n單電子存儲元件n無源二極管n有源雙極晶體管傳感器n單電子探測器n雙方向電子泵n雙重門電路單電子探測器SEM雙重門電路SEM硅納米線在太陽能電池上的應用硅納米線在太陽能電池上的應用n硅納米太陽能電池A new material consisting of clusters of nanocrystalline silicon embedded in an amorphous matrix holds promise for an improved generation of solar

15、 cells that are more stable in sunlight than todays technology.Source: 2003 INquiry2003硅納米線在檢測硅納米線在檢測PH上的應用上的應用,Source: Cui, Y.; Wei, Q.; Park, H.; Lieber, C. M. Science 2001, 293,Silicon nanowires that detect pH硅納米線可實現金屬硅納米線可實現金屬-半導體納米接觸半導體納米接觸Short （0.6 nm ）wires are fully metallized by metal-indu

16、ced gap states resulting in finite conductanceSource: Uzi Landman,1 Robert N. Barnett,1 Andrew G. Scherbakov,1 and Phaedon Avouris2 VOLUME 85, NUMBER 9 PHYSICAL REVIEW LETTERS 28 AUGUST 2000硅納米線應用的最新進展made in the lab of Harvard University chemist Charles Lieber This 300-nanometer-wide silicon wire (

17、left) generates electricity from sunlight. But arrays of microscopic wires could change the economics of solar power by enabling solar cells built from cheap materials such as low-grade silicon or even iron oxide-rust. A number of such cheap materials absorb light and generate electrons, but defects

18、 in the materials usually trap the electrons before they can be collected. Microscopic wires, though, can be made thin enough to allow electrons to slip out easily and generate current, even if the material has defects. And the wires can be long enough to absorb plenty of photons from sunlight hitti

19、ng them at an angle. Such nano-wire solar cells would initially be useful in tiny sensors, or in robots whose electronics might need built-in power. Source: January/February 2008 Issue of Technology Review. 硅納米線的應用最新進展To make solar panels, the microscopic wires could be grown in dense arrays .The image shows a cross section of a silicon-wire array fabricated in the labs of chemist Nathan Lewis and。 physicist Harry -Atwater at Caltech. Each wire is two or three micrometers in diame-ter. Source