- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
Optimum reproduction and characterization of graphene on copper foils by low pressure chemical vapor deposition
摘要： Although the chemical vapor deposition synthesis of scalable graphene was done by many different groups, growing mechanism and optimization of graphene on copper foils has not yet been fully understood under appropriate conditions. In the context of low pressure chemical vapor deposition, annealing of copper can lead to very large and flat grains for uniform formation of monolayer graphene on copper via a combination of H2 and CH4 gases at a substrate temperature of 1000°C. Growing tendency of graphene domains was investigated according to different exposure time and flux of CH4. Graphene was found not to be a uniform coverage of the whole copper surface due to inhomogeneous surface roughness among different copper grains. However, it can be improved more significantly by annealing copper up to near its melting temperature before graphene formation at lower substrate temperature of 1000°C. For this reason, we found that the thermal resistance of our materials acts as a function of the degree of graphene coverage on copper. Our graphene on copper foils was investigated by optical microscopy, Raman spectroscopy, scanning electron microscopy and heat transfer technique.
关键词： Thermal resistance,Interface,Copper foils,LPCVD graphene,Graphene on copper
更新于2025-09-23 15:19:57
-
[IEEE 2019 16th China International Forum on Solid State Lighting & 2019 International Forum on Wide Bandgap Semiconductors China (SSLChina: IFWS) - Shenzhen, China (2019.11.25-2019.11.27)] 2019 16th China International Forum on Solid State Lighting & 2019 International Forum on Wide Bandgap Semiconductors China (SSLChina: IFWS) - Junction Temperature Prediction of the Multi-LED Module with the Modified Thermal Resistance Matrix
摘要： The junction temperature of LEDs is important for its life, reliability and efficacy. The existing transient measurement method of the junction temperature of using transient thermal tester (T3ster) based on the time-resolved measuring with a constant bias current according to the JESD51-14 is able to obtain the LED junction temperature rise based on the known temperature of thermostat module as the heatsink. In practice, without T3ster and the thermostat module, for multi-LED module with multiple heat sources in the luminaries, the thermal resistance matrix needs to be built to realize the thermal transfer between one another such that their junctions temperature raises can be calculated from their thermal power consumption. It is demonstrated that without measurement of the temperature heatsink temperature, the individual junction temperature of LEDs (groups) in multi-LED module with a thermistor (NTC or PTC) on its PCB measuring the local reference temperature can be obtained from the modified N x (N+1) thermal resistance matrix having N LED heat sources and N+1 junction temperature rise. A multi-LED module sample with 3 groups of LEDs has been studied at 5 different ambient temperatures and 2 additional different power combinations using 3 thermal resistance matrices built at 3 different ambient temperatures for comparison. The result showed that the modified method is effective and convenient for measurement of the junction temperature of the multi- LED modules with a similar accuracy comparing to the conventional one in the local reference temperature range of 20~100?C.
关键词： junction temperature,multi-LED module,T3ster,thermal resistance,thermal resistance matrix
更新于2025-09-19 17:13:59
-
Thermal Design Considerations for III-N Vertical-Cavity Surface-Emitting Lasers Using Electro-Opto-Thermal Numerical Simulations
摘要： III-N VCSELs undergo severe self-heating which limits the output optical power. This makes thermal management a critical design consideration. The three most common VCSEL structures (hybrid VCSELs, flip-chip VCSELs and ELOG VCSELs) have been studied using advanced self-consistent electro-opto-thermal numerical simulations. The key geometric and material parameters affecting the thermal resistance of these devices have been identified. Our simulations suggest that some of the proposed solutions and design modifications can increase the maximum optical output power by as much 100%. This manuscript also describes the correct method of using numerical simulation in device design—to predict trends and isolate the key factors affecting device performance.
关键词： electro-opto-thermal simulation,thermal resistance,VCSEL,III-Nitride,laser diode,device modeling
更新于2025-09-19 17:13:59
-
Thermal analysis and heat dissipation improvement for quantum cascade lasers through experiments, simulations, and structure function
摘要： We quantified the thermal resistance of quantum cascade lasers (QCLs) using their structure functions and increased the laser output by employing ridge structures in which thermal resistance was reduced. To improve heat properties, three different QCL devices were prepared as follows. One was a device whose ridge was covered with SiO2, another was a device whose ridge was embedded with Au, and the other was a device whose ridge was embedded with Cu. The temperature distributions were measured with a thermoviewer and were analyzed with three-dimensional simulations. From the results, improved heat dissipation by embedding the ridge was clarified. Furthermore, the structure functions obtained by static mode measurement suggested that the thermal resistance was improved from 9.3 to 6.5 K W?1 by embedding the ridge. As a result of the improvement, the QCL with the Au-embedded ridge had a 1.5-fold higher laser power than the QCL with the SiO2-covered ridge.
关键词： thermal resistance,laser output,heat dissipation,structure function,quantum cascade lasers
更新于2025-09-19 17:13:59
-
Experimental study on cooling of high-power laser diode arrays using hybrid microchannel and slot jet array heat sink
摘要： In this study, a hybrid microchannel and slot jet array heat sink is designed and fabricated to achieve a better thermal performance of the high-power laser diode arrays. A standard commercial laser bar with wavelength of 808 nm is packaged on the heat sink and experiments are performed to assess the cooling performance of the hybrid heat sink. In the experiments, the forward voltage method is used to measure the chip temperature and the structure function method is applied to obtain the thermal resistance of the heat sink. Using the deionized water as coolant, the heat sink deals with a heat flux of up to 506 W/cm2 and the thermal resistance of the heat sink is only 0.23 K/W when the flow rate is 0.8 L/min (The average jet velocity is 13.3 m/s). The optical power can be up to 135.5 W corresponding to the wall plug efficiency of 64.2%. Compared with the published solutions related to cooling similar laser chips, the thermal resistance reduces by over 15%, indicating that this hybrid heat sink is an interesting solution to improve the cooling of the high-power laser diode arrays.
关键词： High-power laser diode array,Cooling,Forward voltage method,Thermal resistance,Optical power
更新于2025-09-16 10:30:52
-
[IEEE 2019 18th International Conference on Optical Communications and Networks (ICOCN) - Huangshan, China (2019.8.5-2019.8.8)] 2019 18th International Conference on Optical Communications and Networks (ICOCN) - Study on Temperature Rise Characteristic of LED Lighting Fixture under Different Conditions
摘要： The temperature rise characteristic of LED lighting fixture under different conditions was studied in the paper. The experimental results showed that the temperature rise of LED lighting fixture under the condition of with cover and no dust was about 1.5 times higher than that of LED lighting fixture under the condition of no cover and with dust. Apparently, the influence of the cover on the heat dissipation of LED lighting fixture was much larger than the dust.
关键词： Cover,Thermal Resistance,Temperature Rise,Heat Dissipation,LED lighting fixture,Dust
更新于2025-09-16 10:30:52
-
[IEEE 2019 25th International Workshop on Thermal Investigations of ICs and Systems (THERMINIC) - Lecco, Italy (2019.9.25-2019.9.27)] 2019 25th International Workshop on Thermal Investigations of ICs and Systems (THERMINIC) - Influence of the use of a thermal pad on electric, optical and thermal parameters of selected power LEDs
摘要： In this paper the influence of the use of thermal pads on electric, optical and thermal parameters of LEDs is considered. For a selected type of power LED operating with a thermal pad and without it, such parameters as: thermal resistance, optical efficiency, power of emitted radiation are measured for selected values of diode forward current. The results of measurements obtained for both manners of diode assembly are compared. Some characteristics illustrating electric, thermal and optical properties of these diodes are shown and discussed. It is proved that the use of a thermal pad makes it possible to achieve better values of operating parameters of the considered power LEDs and lower values of the device internal temperature, which guarantees longer life time of the considered devices.
关键词： power of emitted radiation,thermal resistance,optical efficiency,power LEDs,thermal pad
更新于2025-09-12 10:27:22
-
Modeling of cancer photothermal therapy using near‐infrared radiation and functionalized graphene nanosheets
摘要： Photothermal therapy using near-infrared radiation and local heating agents can induce selective tumor ablation with limited harm to the surrounding normal tissue. Graphene sheets are promising local heating agents due to their strong absorbance of near-infrared radiation. Experimental studies have been conducted to study the heating effect of graphene in photothermal therapy, yet few efforts have been devoted to the quantitative understanding of energy conversion and transport in such systems. Herein, a computational study of cancer photothermal therapy using near-infrared radiation and graphene is presented using a Monte Carlo approach. A three-dimensional model was built with a cancer cell inside a cube of healthy tissue. Functionalized graphene nanosheets were randomly distributed on the surface of the cancer cell. The effects of the concentration and morphology of the graphene nanosheets on the thermal behavior of the system were quantitatively investigated. The interfacial thermal resistance around the graphene sheets, which affects the transfer of heat in the nanoscale, was also varied to probe its effect on the temperature increase of the cancer cell and the healthy tissue. The results of this study could guide researchers to optimize photothermal therapy with graphene, while the modeling approach has the potential to be applied for investigating alternative treatment plans.
关键词： graphene nanosheet,modeling,cancer photothermal therapy,interfacial thermal resistance,near infrared radiation
更新于2025-09-11 14:15:04
-
Analysis on DC and AC Characteristics of Self Heating Effect in Nanowire
摘要： As devices are scaling down aggressively, three-dimensional field-effect transistors (FETs) becomes one of essential factors to obtain high gate controllability in order to reduce leakage current. However, insulators surrounding channel for above the reason block heat emission so that the lattice temperature can increase to the critical levels for devices. This phenomenon, called Self Heating Effect (SHE), can deteriorate device performance significantly. From this point of view, overall study on SHE in 5 nm node Nanowire FET (NWFET) was implemented by simulation. Through analysis on on-current (Ion), thermal resistance (Rth), transient characteristics, the DC and AC characteristics were investigated.
关键词： Thermal Resistance (Rth),Self Heating Effect (SHE),Nanowire FET (NWFET)
更新于2025-09-11 14:15:04
-
[IEEE 2018 IEEE International Symposium on the Physical and Failure Analysis of Integrated Circuits (IPFA) - Singapore (2018.7.16-2018.7.19)] 2018 IEEE International Symposium on the Physical and Failure Analysis of Integrated Circuits (IPFA) - Evaluation of the Thermal Properties for the Design of the Semiconductor Device
摘要： The more semiconductor devices progress, the more importance of caring about heat dissipation from heat generation increase. This is called “Thermal design”. Thermophysical property values like thermal conductivity and thermal expansion coefficient are used as information for thermal design. The specified values in a brochure or literature data of similar materials are usually used as the thermophysical property values for the thermal design. However, when those values are used for simulation, the results may be wrong because an actual measured value such as rate of conduction of heat of an ingredient is different from literature data or the nominal value in many cases. It is thought that there are a lot of cases without considering directionality of an ingredient (anisotropy) and influence of joint interface. We propose that we should measure these values with considering anisotropy, size effect and the bonding state and utilize them for thermal design of electronic materials used in a semiconductor device.
关键词： Thermal diffusivity,Thermal conductivity,Thin film,Thermal resistance,Bonding layer,Anisotropy,Thermal design,Transient thermal measurement
更新于2025-09-10 09:29:36