Measurement of the lateral shift of visible light oblique transmitting from metal film

Ertao Hu

Supervisor: Liangrao Chen

（Department of Optical Science and Engineering, Shanghai, 200433）

Abstract

Negative refraction has been paid much attention due to its potential applications such as: cloak, perfect lens, super resolution, near field storage. In order to get negative refraction, many special artificial structures were made such as: split spring resonators, fish-net structures, array of nano-metal wires ^[1-3]. We note that in most of the artificial structures, noble metals are used especially silver ^[4-8] due to its low loss at optical frequency. By tailoring the dispersion curve of surface plasmons (SPs) of a thin metallic film surrounded by dielectric half-spaces, it is shown that the group velocity of the anti-symmetric mode can be negative^[9]. In our previous works, it was found that negative refraction index can be got at Ag/air interface when the wavelength of the incident light was 473nm, 532nm, 632.8nm and 787nm respectively ^[10]. Wedge-shaped samples were used in order to get the refractive angle directly. However, as is well known that when light oblique incident on a transparent film, the transmission beam will have a lateral shift. This method was used to test the negative refraction properties of metamaterials in microwave or infrared waves ^[11]. But it is short of researches to use this method in optical frequency regime.

If the thickness of the sample is assumed to be 100nm, the refraction index to be -1 and the incident angle to be 45°, the lateral shift will be 141nm. Therefore, it’s very difficult to measure this shift. In our work, an experimental system was set up in order to measure this shift. Details of the system were shown. Some rough results were shown as well.

References:

[1]      John Pendry, Nat. 423, 22 (2003).

[2]      V. M. Shalaev, Nat. Photon 1 (1), 41-48 (2007).

[3]      V. P. Drachev, W. Cai, U. Chettiar, H. K. Yuan, A. K. Sarychev, A. V. Kildishev, G. Klimeck and V. M. Shalaev, Las. Phys. Let. 3 (1), 49-55 (2006).

[4]      Xiebin Fan, Guo Ping Wang, Jeffrey Chi Wai Lee, and C. T. Chan, Phys. Rev. Lett. 97 (7), 073901 (2006).

[5]      G. Nehmetallah, R. Aylo, P. Powers, A. Sarangan, J. Gao, H. Li, A. Achari, and P. P. Banerjee,  Opt. Express 20 (7), 7095 (2012).

[6]      Yi-Jun Jen, Akhlesh Lakhtakia, Ching-Wei Yu, Jheng-Jie Jhou, Wei-Hao Wang, Meng-Jie Lin, Huang-Ming Wu, and Hung-Sheng Liao,  Appl. Phys. Lett. 99 (18), 181117 (2011).

[7]      Konstantin K. Altunin and Oleg N. Gadomsky,  Opt. Communications 285 (5), 816 (2012).

[8]      Nian-Hai Shen, Thomas Koschny, Maria Kafesaki, and Costas M. Soukoulis, Phys. Rev. B 85 (7), 075120 (2012).

[9]      Yongmin Liu, David F. P. Pile, Zhaowei Liu, Dongmin Wu, Cheng Sun, and Xiang Zhang, SPIE, 63231M (2006).

[10]  Y.H. Wu, W. Gu, Y. R. Chen, Z. H. Dai, W. X. Zhou, Yu Xiang Zheng and L. Y. Chen, Appl. Phys.

[11]  Chao Wu, Hongqiang Li, Zeyong Wei, Xiaotong Yu, and C. T. Chan,  Phys. Rev. Lett. 105 (24), 247401 (2010).

Impurity oxygen effects on the local structure of Zr₂Cu at

undercooled liquid and metallic glass

           Guoqing Yue

Supervisor: Songyou Wang

Department of Optical Science and Engineering, Fudan University, Shanghai 200433, China

Abstract:

 Minor alloying additions or microalloying technology has been dominant concepts for developing new metallic crystalline materials scene over the past decade. A remarkable example is the invention of ductile intermetallic Ni₃Al alloys by addition of 0.1 wt% B. Recently, limited work has shown that minor alloying addition dramaticly affects the glass formation and thermal stability of bulk metallic glasses. It is our belief that the minor alloying addition technique in the new century will continue playing an important role in the materials science field.

 Zr-based bulk metallic glasses have attracted much attention due to their unique properties. For widespread application of Zr-based bulk metallic glasses, cost-effective mass production using the industrial raw materials under a low vacuum condition should be the first consideration. Thus, it is unavoidable to understand effects of oxygen on the glass-forming ability of Zr-based bulk metallic glasses.

 In this work, we employd ab initio molecular dynamics simulations to study the effects of oxygen on the local structure in the Zr2Cu undercooled liquid and metallic glass. Radial distribution functions were used to determine interactions between like and unlike bonds and the corresponding interatomic distances. The results showed evidence of short-range order in Zr-O pairs. By using the Honeycutt-Andersen index, Voronoi tessellation method, and the atomistic cluste alignment method, the results revealed that the addition of a low O concentration to Zr-Cu alloys exhibits less icosahedral ordering.

Reference:

[1]Z. Altounian, E. Batalla, and J.O. Strom-Olsen, J. Appl. Phys.61,1(1987)

[2]H. X. Li, J. E. Gao, Z. B. Jiao, Y.Wu, and Z. P. Lu, Appl. Phys. Lett.95,161905(2009)

[3]K. Saksl, J. Saida, A. Inoue, and J. Z. Jiang, Appl. Phys. Lett.83,19(2003)

[4]B. S. Murty, D. H. Ping, A. Inoue, and K. Hono, Appl. Phys. Lett.76, 1(2000)

A study on temperature-dependent optical properties of white tin by spectroscopic ellipsometry

D. X. Zhang

Supervisor: Y. X. Zheng

Department of Optical Science and Engineering, Fudan University, Shanghai 200433, China

Abstract

Tin is commonly known in one of the two allotropic forms. At ambient pressure, the first form of tin is called gray tin (α-Sn), which is a stable phase below 13.2 °C having the cubic, diamond structure.¹At temperature above 13.2 °C, grey tin slowly turns into the second form, white tin (β-Sn), which is a body-centered tetragonal metal.²Due to the sensitive properties of temperature and pressure, the structural, electronic, optical and thermodynamic properties of tin have been the subjects of considerable interest to the scientific community both experimentally and theoretically.^3-5In electronic devices, the melting properties of tin are important as interconnect materials in on-chip and off-chip applications. Several researches indicated that the melting point of tin decreased when their size is reduced to nanometer size.^6-8To study the melting behavior of tin nanoparticle or cluster, it often takes transmission electron microscopy (TEM)⁹, in which the diffraction pattern of crystal structure exhibit the order-disorder transition at the melting point, and nanocalorimeter⁸, by which the latent heat of fusion for tin can be measured.

For optical properties depending on structure with different temperature, the melting properties can be studied by measuring optical constants. Spectroscopic ellipsometry (SE) is routinely used to measure optical properties in microelectronic sciences. Many experimental investigations on optical properties of β-Sn at room temperature have been performed, and a useful way by SE has also been presented.¹⁰  In our work, we present the temperature dependent optical properties of β-Sn by SE in visible light range between 300 nm to 800 nm from room temperature (25 °C) to 250 °C. The variation of optical properties under melting point is mainly from the free carriers and the optical properties totally change upon the melting point for the order-disorder transition. From the results, we present a useful way to determine the melting point of β-Sn thin film by SE measurement.

References:

 ¹       Sadao Adachi, Optical Constants of Crystalline and Amorphous Semiconductors - Numerical Data and Graphical Information. (Kluwer Academic Publishers, Norwell, 1999).

 ²       Edward D. Palik, Handbook of Optical Constants of Solids III. (Academic Press, San Diego, 1998).

 ³       R. Ravelo and M. Baskes, "Equilibrium and thermodynamic properties of grey, white, and liquid tin," Phys Rev Lett 79 (13), 2482-2485 (1997).

 ⁴       G. Jézéquel, J. C. Lemonnier and J. Thomas, "Optical properties of white tin films between 2 and 15eV," J Phys F:Metal Phys 7 (12), 2613-2621 (1977).

 ⁵       C. Yu, J. Y. Liu and H. Lu et al., "Ab initio calculation of the properties and pressure induced transition of Sn," Solid State Commun 140 (11-12), 538-543 (2006).

 ⁶       H. J. Jiang, K. S. Moon and H. Dong et al., "Size-dependent melting properties of tin nanoparticles," Chem Phys Lett 429 (4-6), 492-496 (2006).

 ⁷       Y. H. Jo, I. Jung and C. S. Choi et al., "Synthesis and characterization of low temperature Sn nanoparticles for the fabrication of highly conductive ink," Nanotechnology 22 (22570122) (2011).

 ⁸       S. L. Lai, J. Y. Guo and V. Petrova et al., "Size-dependent melting properties of small tin particles: Nanocalorimetric measurements," Phys Rev Lett 77 (1), 99-102 (1996).

 ⁹       M. Takagi, "Electron-diffraction study of liquid-solid transition of thin metal films," J Phys Soc Jpn 9 (3), 359-363 (1954).

¹⁰       K. Takeuchi and S. Adachi, "Optical properties of beta-Sn films," J Appl Phys 105 (0735207) (2009).

Deposition of carbon nitride nanocone (CNNC) arrays with PLD and GPCVD

Xujun Liu

Supervisor: Ning Xu

Department of Optical Science and Engineering, Fudan University

Abstract

Carbon nitride(CN_x) films have attracted great interest since Liu and Cohen predicted the hypothetical β-C₃N₄ compound with properties comparable to diamond. In addition to the high hardness, CN_x have the characteristics of wear-resistant, anti-corrosion, wide bandgap, high temperature and high thermal conductivity, so carbon nitride had a good prospect in the field of machining,field emission material, semiconductor and optical device.

CN_x have been synthesised by various techniques such as, RF plasma assisted PLD,ion beam assisted deposition, plasma enhanced hot filament chemical vapor deposition, dielectric barrier discharge. Here, carbon nitride nanocone (CNNC) arrays were fabricated on Si(100) by PLD and GPCVD.To begin with, Ni intermediate layers of about 100 nm were deposited by pulsed laser deposition (PLD) on smooth or scratched Si(100) wafers.Then,a CH4/N2 mixed gas was led into the plasma source and the abnormal glow discharge began for growing CNNC arrays.And it was found that experimental parameters such as discharge gas flow ratio, discharge voltage and current could effect on the growth of carbon nitride nanocons.

References

[1] A. Y. Liu, M. L. Cohen, Science. 245,841(1989).

[2] A. Y. Liu, M. L. Cohen,Phys. Rev. B.41,10727(1989).

[3] D. M.Teter, R. J. Hemley, Science. 271,53(1996).

[4] A. Majumdar, R. Hippler, Review of Scientific Instruments.78, 075103(2007).

[5] Wei Hu,Ning Xu,et alJournal of Electronic Materials, Vol. 39, No. 4, (2010).

[6] E. Cappelli,S. Orlando, D.M. Trucchi, A. Bellucci, V. Valentini,A. Mezzi, S. Kaciulis,Applied Surface Science257, 5175 (2011).

[7] U. Martens, H. C. Thejaswini, A. Majumdar, R. Hippler,Plasma Process. Polym.9, 647(2012).

[8] S. Wei et al. Surface & Coatings Technology 206,3944 (2012) .

Study of silicon solar cell Efficiency Enhancement by using PL conversion materials: Silicon Nano-crystals & Mn:ZnSe quantum dots

Reporter: Hao Hongchen

Supervisor: Lu Min

Abstract:

Spectrum modification is suggested to be a promising method to overcome the classical efficiency limits of silicon solar cells causing by mismatching between solar spectrum and response curve of the cell. There are three way to modify the solar spectrum to match with the silicon solar cell response curve: down-conversion (cutting one photon into two low energy photons), up-conversion (combining low energy photons into one high energy photon) and Photoluminescence (PL)-conversion (shifting photon into wavelength better accepted by silicon solar cell). We researched two kind of PL-conversion materials: silicon Nano-crystals with multilayer structural and Mn:ZnSe quantum dot-dropped PLMA thin film.

This report presents the result of efficiency enhancement by using these two conversion materials. We also assessed precisely the contribution of PL conversion to solar cell efficiency enhancement under an all-solar-spectrum condition by using multiple quantum efficiency measurements, which has never been done before. We try to raise a method to evaluate the effect of conversion materials.

References

1. C. Strümpel, M. McCann, et al. Solar Energy Materials & Solar Cells 91 (2007)
2. V. Švrček, I. Pelant, et al. Materials Science and Engineering C 19(2002)
3. V. Švrček, A. Slaoui, J.-C. Muller Thin Solid Films 451 –452 (2004)
4. T. Trupke, R. A. Bardos, et al. Applied Physics Letters 87, 093503 (2005)
5. Hsin-Chu Chen, Chien-Chung Lin, et al. Solar EnergyMaterials&SolarCells104(2012)