Article

Sub-wavelength temperature probing in near-field laser heating by particles

Department of Mechanical Engineering, Iowa State University, 2010 Black Engr. Bldg., Ames, Iowa 50011, USA.
Optics Express (Impact Factor: 3.53). 06/2012; 20(13):14152-67. DOI: 10.1364/OE.20.014152
Source: PubMed

ABSTRACT This work reports on the first time experimental investigation of temperature field inside silicon substrates under particle-induced near-field focusing at a sub-wavelength resolution. The noncontact Raman thermometry technique employing both Raman shift and full width at half maximum (FWHM) methods is employed to investigate the temperature rise in silicon beneath silica particles. Silica particles of three diameters (400, 800 and 1210 nm), each under four laser energy fluxes of 2.5 × 10(8), 3.8 ×10(8), 6.9 ×10(8) and 8.6 ×10(8) W/m(2), are used to investigate the effects of particle size and laser energy flux. The experimental results indicate that as the particle size or the laser energy flux increases, the temperature rise inside the substrate goes higher. Maximum temperature rises of 55.8 K (based on Raman FWHM method) and 29.3K (based on Raman shift method) are observed inside the silicon under particles of 1210 nm diameter with an incident laser of 8.6 × 10(8) W/m(2). The difference is largely due to the stress inside the silicon caused by the laser heating. To explore the mechanism of heating at the sub-wavelength scale, high-fidelity simulations are conducted on the enhanced electric and temperature fields. Modeling results agree with experiment qualitatively, and discussions are provided about the reasons for their discrepancy.

0 Followers
 · 
139 Views
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: A normal full-contact graphene-substrate interface has been reported to have a thermal conductance in the order of 108 Wm(-2)K(-1). The reported work used a sandwiched structure to probe the interface energy coupling, and the phonon behavior in graphene is significantly altered in an undesirable way. Here we report an intriguing study of energy coupling across unconstrained graphene-substrate interfaces. Using novel Raman-based dual thermal probing, we directly measured the temperature drop across the few-nm gap interface that is subjected to a local heat flow induced by a second laser beam heating. For the first time, we determined the thermal conductance (Gt) as 183±10 and 266±10 Wm(-2)K(-1) for graphene/Si and graphene/SiO2 interfaces. This Gt is five orders of magnitude smaller than that of full interface contact. It reveals the remarkable effect of graphene corrugation on interface energy coupling. The measurement result is elucidated by atomistic modeling of local corrugation and energy exchange. By decoupling of graphene's thermal and mechanical behavior, we obtained the stress-induced Raman shift of graphene at around 0.1 cm(-1) or less, suggesting extremely loose interface mechanical coupling. The interface gap variation is evaluated quantitatively based on corrugation-induced Raman enhancement. The interface gap could change as large as 1.8 nm when the local thermal equilibrium is destroyed.
    ACS Applied Materials & Interfaces 01/2014; 6(4). DOI:10.1021/am405388a · 5.90 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Iindex of published papers on thermology or temperature measurement Voluime 4: 2011 to 2013
  • [Show abstract] [Hide abstract]
    ABSTRACT: The effects of CdSe nanocrystal (NC) shape and size on the temperature sensitivity of the Raman shift have been investigated, for the interest of Raman thermometry using NCs. For spherical CdSe NCs of diameters 2.8 nm, 3.6 nm, and 4.4 nm, the temperature sensitivities are −0.0131 cm−1/K, −0.0171 cm−1/K, and −0.0242 cm−1/K, respectively. This trend indicates that as the diameter increases, the effect of increasing phonon anharmonicity dominates over the effect of the decreasing thermal expansion coefficient. On the other hand, triangular NCs with a size of 4.2 nm and elongated NCs of a dimension of 4.6 nm by 14 nm show temperature sensitivities of −0.0182 cm−1/K and −0.0176 cm−1/K, respectively. This trend indicates that in non-spherical shape NCs, the effect of decreasing thermal expansion coefficient dominates over the effect of slightly increasing phonon anharmonicity. The selection of NCs for Raman thermometry should depend on the specific requirements of temperature sensitivity, spatial resolution, and response time.
    Applied Physics Letters 08/2013; 103(8). DOI:10.1063/1.4819170 · 3.52 Impact Factor

Full-text

Download
124 Downloads
Available from
Jun 14, 2014
Available from