Photothermal examination of buried layers

1986 ◽  
Vol 64 (9) ◽  
pp. 1291-1292 ◽  
Author(s):  
J. Baumann ◽  
R. Tilgner
Keyword(s):  
Thermal Properties ◽  
Heat Source ◽  
Thermal Wave ◽  
Diffusion Length ◽  
Thermal Waves ◽  
Layer Sample ◽  
Buried Layer ◽  
Buried Layers ◽  
Periodic Illumination

The influence of a buried layer within a sample on the propagation of thermal waves is determined by measuring the phase and amplitude of the photothermal signal during periodic illumination. The results are in agreement with the calculation that follows a thermal-wave approach involving a three-layer sample and a Lambert–Beer-like distribution of the heat source in the covering layer. In this way determination of the thickness or thermal properties of buried layers even much thinner than their thermal-diffusion length is possible.

Ion Implantation Monitoring of GaAs Using Thermal Waves

1993 ◽  
Vol 316 ◽  
Author(s):  
R. Garcia ◽  
E. J. Jaquez ◽  
R.J. Culbertson ◽  
C. D'Acosta ◽  
C. Jasper
Keyword(s):  
Activation Energy ◽  
Thermal Properties ◽  
Ion Implantation ◽  
Diffusion Process ◽  
Thermal Wave ◽  
Room Temperature ◽  
Implantation Dose ◽  
Thermal Waves ◽  
Crystal Imperfections ◽  
Logarithmic Decay

ABSTRACTLaser modulated thermoreflectivity, also called thermal wave technology, has been used in recent years to monitor ion implantation dose by monitoring the damage due to implantation. The thermal properties which are affected by lattice perturbations and other crystal imperfections are tracked by this technique. A gauge capability study was performed on the Thermawave TP300 for monitoring ion implantation of GaAs wafers. The results are presented. In order to determine the sensitivity of the technique to changes in dose, a matrix of GaAs and Si wafers was measured. During this study a downward trend was observed in the repeatability of our results. It is shown that damage to a sample during implantation will relax to a certain degree at room temperature. This damage relaxation can take up to 80 hours at room temperature and can be observed using thermal waves. It is shown that “hot wafer decay” follows a logarithmic decay which is indicative of a diffusion process. At 180°C the decay lasts less than 1 minute which indicates that the defects causing this phenomenon have a low activation energy.

Thermal wave imaging of microelectronics

2016 ◽  
Vol 138 (2) ◽  
Author(s):  
Miguel Goni ◽  
Aaron J. Schmidt
Keyword(s):  
Thermal Properties ◽  
Surface Temperature ◽  
Thermal Wave ◽  
High Frequency ◽  
Low Frequency ◽  
Thermal Response ◽  
Glass Layer ◽  
Thermal Waves ◽  
Frequency Wave ◽  
Thermal Penetration Depth

Thermal waves can reveal thermal properties of different layers forming a multilayer structure. If the thickness of each layer is known, specific ranges of thermal wave frequencies can be implemented to study the thermal response of a specific number of layers and eventually extract the thermal properties of individual layers. As a first approach this idea can be simplified by means of the thermal penetration depth parameter, δ. The thermal penetration depth is defined as, δ=k/πCf, where k and C are respectively the thermal conductivity and volumetric heat capacity of the material carrying the thermal wave and f is the frequency of the thermal wave. From this expression it can be seen how it is possible to constrain the material thermal response to a desired depth by controlling the frequency. Thus, using high enough frequencies, the top layer properties would be measured first. Decreasing the thermal wave frequency by an appropriate amount would include the next layer in the thermal response. Since the properties of the first layer are now known, it would be possible to extract the properties of the current layer. The measurement would continue in a similar fashion for the remaining layers. Frequency domain thermoreflectance (FDTR) can be used to generate thermal waves. In this technique, a periodically modulated continuous wave laser (red pump beam) provides the periodic heat flux input into the material while a second laser (green probe beam) monitors the surface temperature through a proportional change of the surface reflectivity. The measured value is the phase lag (degrees) between the incoming thermal wave and the surface temperature response. In this study, an FDTR system was used in conjunction with a piezo stage to obtain thermal images of two different multilayer structures. The first one consisted of a CPU chip formed mainly by layers of SiO2 and Cu. The second case consisted of a TFT LCD screen from a mobile device. Regarding the CPU chip, the low frequency thermal wave travelled well past the second layer of Cu wires and provided thermal information about the bottom layers of the chip. In contrast, the high frequency wave could not penetrate through the second layer, which resulted in a more sensitive response upon the Cu wires close to the surface. A similar phenomenon occurred with the LCD screen. In this case the top layer was a glass layer used to sandwich the liquid crystal and the second layer is composed of the ITO electrodes that provide the electric field. It can be observed how the high frequency wave did not penetrate through the top glass layer providing no thermal information about the bottom layer as opposed to the low frequency wave, which clearly shows the ITO electrodes. The estimated thermal penetration depths displayed on top of each image were calculated using the equation provided before with known thermal properties of SiO2, Cu and ITO.

Determination of the thermal properties of leaves by non-invasive contact‑free laser probing

2016 ◽  
Vol 217 ◽  
pp. 100-108 ◽  
Author(s):  
J.F. Buyel ◽  
H.M. Gruchow ◽  
N. Tödter ◽  
M. Wehner
Keyword(s):  
Thermal Properties ◽  
Non Invasive ◽  
Laser Probing ◽  
Contact Free

scholarly journals Determination of a spacewise dependent heat source

2007 ◽  
Vol 209 (1) ◽  
pp. 66-80 ◽  
Author(s):  
Tomas Johansson ◽  
Daniel Lesnic
Keyword(s):  
Heat Source

Analysis of Tempering and Rehardening for Grinding of Hardened Steels

1991 ◽  
Vol 113 (4) ◽  
pp. 388-394 ◽  
Author(s):  
O. B. Fedoseev ◽  
S. Malkin
Keyword(s):  
Thermal Properties ◽  
Heat Source ◽  
Hardened Steel ◽  
Temperature History ◽  
Hardness Distribution ◽  
Temperature Dependent ◽  
Thermally Activated ◽  
Reaction Equations ◽  
Rate Controlling Step ◽  
Good Agreement

An analysis is presented to predict the hardness distribution in the subsurface of hardened steel due to tempering and rehardening associated with high temperatures generated in grinding. The grinding temperatures are modeled with a triangular heat source at the grinding zone and temperature-dependent thermal properties. The temperature history, including the effect of multiple grinding passes, is coupled with thermally activated reaction equations for tempering and for reaustenitization which is the rate controlling step in rehardening. Experimental results from the literature are found to be in good agreement with the analytical predictions.

Nanofluids: Synthesis, Heat Conduction, and Extension

2009 ◽  
Vol 131 (3) ◽  
Author(s):  
Liqiu Wang ◽  
Xiaohao Wei
Keyword(s):  
Heat Conduction ◽  
Olive Oil ◽  
Thermal Wave ◽  
Thermal Waves ◽  
Water Conductivity ◽  
Conductivity Enhancement ◽  
Chemical Solution Method ◽  
New Type ◽  
Fourier Heat Conduction ◽  
Two Phases

We synthesize eight kinds of nanofluids with controllable microstructures by a chemical solution method (CSM) and develop a theory of macroscale heat conduction in nanofluids. By the CSM, we can easily vary and manipulate nanofluid microstructures through adjusting synthesis parameters. Our theory shows that heat conduction in nanofluids is of a dual-phase-lagging type instead of the postulated and commonly used Fourier heat conduction. Due to the coupled conduction of the two phases, thermal waves and possibly resonance may appear in nanofluid heat conduction. Such waves and resonance are responsible for the conductivity enhancement. Our theory also generalizes nanofluids into thermal-wave fluids in which heat conduction can support thermal waves. We emulsify olive oil into distilled water to form a new type of thermal-wave fluids that can support much stronger thermal waves and resonance than all reported nanofluids, and consequently extraordinary water conductivity enhancement (up to 153.3%) by adding some olive oil that has a much lower conductivity than water.

A-Si:H Ambipolar Diffusion Length and Effective Lifetime Measured by Flying Spot Technique (FST)

1991 ◽  
Vol 219 ◽  
Author(s):  
M. Vieira ◽  
R. Martins ◽  
E. Fortunato ◽  
F. Soares ◽  
L. Guimaraes
Keyword(s):  
Laser Beam ◽  
Transient Analysis ◽  
Diffusion Length ◽  
Transport Equations ◽  
Ambipolar Diffusion ◽  
Schottky Barriers ◽  
Effective Lifetime ◽  
Asymmetrical Distribution ◽  
Flying Spot

ABSTRACTThe determination of the ambipolar diffusion length, L*, and the effective lifetime, τ*, in p/i and a-Si:H Schottky barriers (ITO/p/a-Si:H/Al-Si; Cr/a-Si:H/Cr/Ag) have been determined by Flying Spot Technique, FST. This technique consists in the transient analysis of the photocurrent/photopotential induced by a laser beam that moves perpendicularly to the structure with a constant motion ratio, at different velocities. Taking into account the competition between the diffusion/drift velocities of the excess carriers and the velocity of the flying spot, it is possible to solve the transport equations and to compute separately L* and τ*, from the asymmetrical distribution responses.

Sign in / Sign up

Export Citation Format

Share Document