Pub Date : 2016-07-21DOI: 10.1109/ITHERM.2016.7517571
W. Tong, Chenlong Wu, K. Toh, F. Duan
An experimental investigation of pool boiling on the heat spreader lid surface of a real central processing unit (CPU) is presented in this paper. A highly wetting dielectric liquid, Novec 7100, was employed as coolant. The nucleate boiling process was observed and recorded through a high-speed camera. The boiling curves of saturated Novec 7100 liquid on the CPU heat spreader lid were obtained. The quantities used to characterize bubble dynamics, such as active nucleation site density, bubble departure diameter and bubble departure frequency, were measured through the high-speed video at different wall heat fluxes. The averaged values of all these quantities have increasing trends with increasing wall heat flux. The relationships between quantities and heat flux can be further embedded into nucleate boiling heat transfer models for validation.
{"title":"Experimental study of bubble dynamics in highly wetting dielectric liquid pool boiling through high-speed video","authors":"W. Tong, Chenlong Wu, K. Toh, F. Duan","doi":"10.1109/ITHERM.2016.7517571","DOIUrl":"https://doi.org/10.1109/ITHERM.2016.7517571","url":null,"abstract":"An experimental investigation of pool boiling on the heat spreader lid surface of a real central processing unit (CPU) is presented in this paper. A highly wetting dielectric liquid, Novec 7100, was employed as coolant. The nucleate boiling process was observed and recorded through a high-speed camera. The boiling curves of saturated Novec 7100 liquid on the CPU heat spreader lid were obtained. The quantities used to characterize bubble dynamics, such as active nucleation site density, bubble departure diameter and bubble departure frequency, were measured through the high-speed video at different wall heat fluxes. The averaged values of all these quantities have increasing trends with increasing wall heat flux. The relationships between quantities and heat flux can be further embedded into nucleate boiling heat transfer models for validation.","PeriodicalId":426908,"journal":{"name":"2016 15th IEEE Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm)","volume":"263 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2016-07-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116178586","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2016-07-21DOI: 10.1109/ITHERM.2016.7517735
U. S. Kumar, V. Rao
Self-heating effects of sub-20-nm fin-shaped FET (FinFET) technologies are studied and analyzed in this work using well-calibrated TCAD 3-D electro thermal simulations. We show that the thermal performance characteristics can be accurately measured from the ac capacitance method using simple extraction techniques. The extracted thermal time constants are in nanoseconds range, and show a decrease with scaling. This is because of the increase in the surface area to volume ratio of the fins in FinFETs. The thermal resistance decreases with increase in the input power owing to the spread of the heated volume. Bulk FinFETs have a less thermal resistance as compared with SOI FinFETs because of the effectiveness of its lower fin region. Thermal resistance increases with reduction in fin pitch and increase in the number of fins. Drain current degradation because of self-heating effects, decreases with scaling. This is because the threshold voltage dependence on temperature dominates the mobility or saturation velocity dependence.
{"title":"Thermal performance of nano-scale SOI and bulk FinFETs","authors":"U. S. Kumar, V. Rao","doi":"10.1109/ITHERM.2016.7517735","DOIUrl":"https://doi.org/10.1109/ITHERM.2016.7517735","url":null,"abstract":"Self-heating effects of sub-20-nm fin-shaped FET (FinFET) technologies are studied and analyzed in this work using well-calibrated TCAD 3-D electro thermal simulations. We show that the thermal performance characteristics can be accurately measured from the ac capacitance method using simple extraction techniques. The extracted thermal time constants are in nanoseconds range, and show a decrease with scaling. This is because of the increase in the surface area to volume ratio of the fins in FinFETs. The thermal resistance decreases with increase in the input power owing to the spread of the heated volume. Bulk FinFETs have a less thermal resistance as compared with SOI FinFETs because of the effectiveness of its lower fin region. Thermal resistance increases with reduction in fin pitch and increase in the number of fins. Drain current degradation because of self-heating effects, decreases with scaling. This is because the threshold voltage dependence on temperature dominates the mobility or saturation velocity dependence.","PeriodicalId":426908,"journal":{"name":"2016 15th IEEE Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm)","volume":"404 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2016-07-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133540194","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2016-07-21DOI: 10.1109/ITHERM.2016.7517613
A. Alpert, R. Luo, M. Asheghi, E. Pop, K. Goodson
A simple analytical model is presented, which predicts the energy required for a reset operation in a phase change memory (PCM) device with a graphene monolayer between a bottom metallic electrode (BEC) and Ge2Sb2Te5 (GST) chalcogenide layer. The graphene effectively adds thermal boundary resistance between the GST and metal electrode, limiting the parasitic loss of heat into the electrode. Additionally, the model considers the effects of electrode size and Peltier heating, both to the steady state and transient performance. The graphene monolayer reduces the reset energy by a factor of between 2 and 10 over the direct electrode-GST interface, the Peltier effect reduces the reset energy by a factor of approximately 4, and scaling the size of the electrode results in better than exponential energy reduction.
{"title":"Analytical model of graphene-enabled ultra-low power phase change memory","authors":"A. Alpert, R. Luo, M. Asheghi, E. Pop, K. Goodson","doi":"10.1109/ITHERM.2016.7517613","DOIUrl":"https://doi.org/10.1109/ITHERM.2016.7517613","url":null,"abstract":"A simple analytical model is presented, which predicts the energy required for a reset operation in a phase change memory (PCM) device with a graphene monolayer between a bottom metallic electrode (BEC) and Ge2Sb2Te5 (GST) chalcogenide layer. The graphene effectively adds thermal boundary resistance between the GST and metal electrode, limiting the parasitic loss of heat into the electrode. Additionally, the model considers the effects of electrode size and Peltier heating, both to the steady state and transient performance. The graphene monolayer reduces the reset energy by a factor of between 2 and 10 over the direct electrode-GST interface, the Peltier effect reduces the reset energy by a factor of approximately 4, and scaling the size of the electrode results in better than exponential energy reduction.","PeriodicalId":426908,"journal":{"name":"2016 15th IEEE Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm)","volume":"15 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2016-07-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115263004","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2016-07-21DOI: 10.1109/ITHERM.2016.7517551
Dae-Suk Kim, B. Han, A. Bar-Cohen
An inverse approach is developed and implemented to quantify the resistance of the die-attach thermal interface (DTI) in high power light emitting diodes (LEDs). The transient time domain dominated by the resistance of the DTI is selected first using a hybrid analytical/numerical solution. Then, the resistance of the DTI is determined inversely from the experimental data over the predetermined transient time domain using numerical modeling. The results confirm that the proposed approach offers a measurement accuracy of 0.01 K/W.
{"title":"Inverse approach to characterize die-attach thermal interface of light emitting diodes","authors":"Dae-Suk Kim, B. Han, A. Bar-Cohen","doi":"10.1109/ITHERM.2016.7517551","DOIUrl":"https://doi.org/10.1109/ITHERM.2016.7517551","url":null,"abstract":"An inverse approach is developed and implemented to quantify the resistance of the die-attach thermal interface (DTI) in high power light emitting diodes (LEDs). The transient time domain dominated by the resistance of the DTI is selected first using a hybrid analytical/numerical solution. Then, the resistance of the DTI is determined inversely from the experimental data over the predetermined transient time domain using numerical modeling. The results confirm that the proposed approach offers a measurement accuracy of 0.01 K/W.","PeriodicalId":426908,"journal":{"name":"2016 15th IEEE Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm)","volume":"40 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2016-07-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127140265","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2016-07-21DOI: 10.1109/ITHERM.2016.7517616
M. Seymour
The data center industry is focused on improving the energy efficiency of modern data centers due to their increasing energy costs and consumption, and the consequent carbon emissions. However, there is a lack of adopted process or metrics for data center cooling performance; this potentially puts facilities at risk from the unseen consequences of focusing on energy efficiency alone. The challenge for a data center operator is how to assess cooling performance. The facility's design likely makes assumptions about what IT equipment will be installed and how it will be configured that are not reflected in the operational configuration. This paper uses engineering simulation based on computational fluid dynamics (CFD) to show the relationship between the quantity of IT equipment that may be safely installed and the efficiency of the cooling system. Both are affected by changes to the cooling system settings and any IT equipment/applications deployed. The IT heat load and airflow requirement varies in legacy/enterprise style data centers and virtualized/cloud data centers alike, and this affects the cooling requirement. Using engineering simulation to predict the consequences of change provides a valuable complementary tool to the operator: it gives insight on how to avoid lost capacity, and helps them to better configure their facility when making decisions on infrastructure, IT deployment, or - in a virtualized environment - application deployment.
{"title":"Is energy efficiency enough? Filling the engineering gap in data center design and operation","authors":"M. Seymour","doi":"10.1109/ITHERM.2016.7517616","DOIUrl":"https://doi.org/10.1109/ITHERM.2016.7517616","url":null,"abstract":"The data center industry is focused on improving the energy efficiency of modern data centers due to their increasing energy costs and consumption, and the consequent carbon emissions. However, there is a lack of adopted process or metrics for data center cooling performance; this potentially puts facilities at risk from the unseen consequences of focusing on energy efficiency alone. The challenge for a data center operator is how to assess cooling performance. The facility's design likely makes assumptions about what IT equipment will be installed and how it will be configured that are not reflected in the operational configuration. This paper uses engineering simulation based on computational fluid dynamics (CFD) to show the relationship between the quantity of IT equipment that may be safely installed and the efficiency of the cooling system. Both are affected by changes to the cooling system settings and any IT equipment/applications deployed. The IT heat load and airflow requirement varies in legacy/enterprise style data centers and virtualized/cloud data centers alike, and this affects the cooling requirement. Using engineering simulation to predict the consequences of change provides a valuable complementary tool to the operator: it gives insight on how to avoid lost capacity, and helps them to better configure their facility when making decisions on infrastructure, IT deployment, or - in a virtualized environment - application deployment.","PeriodicalId":426908,"journal":{"name":"2016 15th IEEE Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm)","volume":"12 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2016-07-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129775538","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2016-07-21DOI: 10.1109/ITHERM.2016.7517682
Seungho Mok, Satish Kumar, Ronald R. Hutchins, Y. Joshi
With the rise of acceptable operating temperatures for information technology (IT) equipment, using ambient air has been a growing trend for data centers. In this computational study, a thermal wheel is used as a rotary air-to-air heat exchanger extracting heat from IT equipment and dissipating it to the ambient. The wheel is made of a metallic honeycomb material that enables air to pass through while convectively transferring heat. A computational model has been developed to calculate the volumetric air flow rate required for an assigned cooling load. When the ambient temperature is too high, direct expansion cooling is used as a secondary approach and modeled in building energy usage estimation software, EnergyPlus. The integrated computational model calculates overall power usage effectiveness (PUE) for data centers. Using weather data for a specific location, PUEs for several different climates can be obtained. Even without considering the energy savings that is produced through less air quality and humidity control, for a cooling load of 400 kW, it was found that overall PUE can be as low as 1.10 in Helsinki, Finland and 1.20 in Atlanta, Georgia. The presented model can be used to determine the system performance with varying location, cooling load, and regenerative heat exchanger parameters.
{"title":"Impact of a rotary regenerative heat exchanger on energy efficiency of an air cooled data center","authors":"Seungho Mok, Satish Kumar, Ronald R. Hutchins, Y. Joshi","doi":"10.1109/ITHERM.2016.7517682","DOIUrl":"https://doi.org/10.1109/ITHERM.2016.7517682","url":null,"abstract":"With the rise of acceptable operating temperatures for information technology (IT) equipment, using ambient air has been a growing trend for data centers. In this computational study, a thermal wheel is used as a rotary air-to-air heat exchanger extracting heat from IT equipment and dissipating it to the ambient. The wheel is made of a metallic honeycomb material that enables air to pass through while convectively transferring heat. A computational model has been developed to calculate the volumetric air flow rate required for an assigned cooling load. When the ambient temperature is too high, direct expansion cooling is used as a secondary approach and modeled in building energy usage estimation software, EnergyPlus. The integrated computational model calculates overall power usage effectiveness (PUE) for data centers. Using weather data for a specific location, PUEs for several different climates can be obtained. Even without considering the energy savings that is produced through less air quality and humidity control, for a cooling load of 400 kW, it was found that overall PUE can be as low as 1.10 in Helsinki, Finland and 1.20 in Atlanta, Georgia. The presented model can be used to determine the system performance with varying location, cooling load, and regenerative heat exchanger parameters.","PeriodicalId":426908,"journal":{"name":"2016 15th IEEE Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm)","volume":"2 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2016-07-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131116919","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2016-07-21DOI: 10.1109/ITHERM.2016.7517659
S. Lei, I. Mathews, J. Camus, S. Bensalem, M. Djouadi, A. Shen, G. Duan, R. Enright
In the paper, we aim to solve the thermal problems appearing in integrated silicon photonics by using high thermal conductivity Aluminium Nitride (ALN) as a thermal spreading layer located around the ridge of a hybrid III-V laser on silicon in comparison to the existing encapsulation material benzocyclobutene (BCB). Here, to facilitate the design of reliable hybrid semiconductor lasers, we first develop and implement a multiphysics electro-thermo-mechanical model within a finite element environment COMSOL. A phenomenological model of laser operation is used to numerically capture all the thermal and electrical characteristics of the lasers. In terms of the hybrid devices, the simulated thermal resistance agrees well with our device measurements presented in Part 1 of this work. We also demonstrate that the use of the ALN heat spreader can significantly reduce the thermal resistance. Moreover, a linear elastic model is employed for a mechanical analysis of the entire laser structure. The maximum allowable stress is estimated using the Christensen criterion. We find that the process-dependent residual stress dictates the device stress field. In the current design, the BCB encapsulation layer is at risk of failure around the InP waveguide. For AlN spreaders, lower film processing temperatures are key to reduce the stress in the deposited film. We further perform a parametric study on Tref to determine the maximum allowable deposition temperature of AlN/BCB. The simulations suggest that Tref should not exceed 59 °C and 69 °C for ALN and BCB respectively to avoid mechanical failure in the devices.
{"title":"ALN thin-films as heat spreaders in III–V photonics devices Part 2: Simulations","authors":"S. Lei, I. Mathews, J. Camus, S. Bensalem, M. Djouadi, A. Shen, G. Duan, R. Enright","doi":"10.1109/ITHERM.2016.7517659","DOIUrl":"https://doi.org/10.1109/ITHERM.2016.7517659","url":null,"abstract":"In the paper, we aim to solve the thermal problems appearing in integrated silicon photonics by using high thermal conductivity Aluminium Nitride (ALN) as a thermal spreading layer located around the ridge of a hybrid III-V laser on silicon in comparison to the existing encapsulation material benzocyclobutene (BCB). Here, to facilitate the design of reliable hybrid semiconductor lasers, we first develop and implement a multiphysics electro-thermo-mechanical model within a finite element environment COMSOL. A phenomenological model of laser operation is used to numerically capture all the thermal and electrical characteristics of the lasers. In terms of the hybrid devices, the simulated thermal resistance agrees well with our device measurements presented in Part 1 of this work. We also demonstrate that the use of the ALN heat spreader can significantly reduce the thermal resistance. Moreover, a linear elastic model is employed for a mechanical analysis of the entire laser structure. The maximum allowable stress is estimated using the Christensen criterion. We find that the process-dependent residual stress dictates the device stress field. In the current design, the BCB encapsulation layer is at risk of failure around the InP waveguide. For AlN spreaders, lower film processing temperatures are key to reduce the stress in the deposited film. We further perform a parametric study on Tref to determine the maximum allowable deposition temperature of AlN/BCB. The simulations suggest that Tref should not exceed 59 °C and 69 °C for ALN and BCB respectively to avoid mechanical failure in the devices.","PeriodicalId":426908,"journal":{"name":"2016 15th IEEE Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm)","volume":"90 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2016-07-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115930308","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2016-07-21DOI: 10.1109/ITHERM.2016.7517625
Christopher M. Duron, S. Bhavnani, V. Narayanan, Jacob R. Morris
As phase change, specifically boiling becomes an ever more popular and advanced mechanism for cooling electronics, efforts must be made to find methods of increasing the thermal performance of condensers.
{"title":"Condensate mobility actuated by microsurface topography and wettability modifications","authors":"Christopher M. Duron, S. Bhavnani, V. Narayanan, Jacob R. Morris","doi":"10.1109/ITHERM.2016.7517625","DOIUrl":"https://doi.org/10.1109/ITHERM.2016.7517625","url":null,"abstract":"As phase change, specifically boiling becomes an ever more popular and advanced mechanism for cooling electronics, efforts must be made to find methods of increasing the thermal performance of condensers.","PeriodicalId":426908,"journal":{"name":"2016 15th IEEE Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm)","volume":"18 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2016-07-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122839163","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2016-07-20DOI: 10.1109/ITHERM.2016.7517520
S. Hirasawa, T. Nakajima, Tetsuya Urimoto, Yuya Tsujimoto, Y. Takeuchi, T. Kawanami, K. Shirai
Enhancement of evaporation heat transfer performance is important for cooling of electronic devices. Evaporation heat transfer coefficient of two types of porous surfaces supplied with water liquid film was studied experimentally. First porous surface was multi layers of meshed plates with micro-channel of 0.3 mm width. Thin water liquid film was supplied to the porous surface by bubbles. Evaporation heat transfer coefficient of the porous surface with one or two layers of meshed plates was 8×104 W/m2K and it was higher than pool boiling heat transfer coefficient. Second porous surface was 1 mm thickness of glass-beads of 0.4 mm in diameter on a heated cupper plate. Water was supplied to the porous layer at the center of the plate. Evaporation heat transfer coefficient was 1000 W/m2K after water was supplied. Evaporation heat transfer coefficient increased to 7000 W/m2K before appearance of dry portion on the plate, because water film thickness in the porous layer was thin.
{"title":"Experiment on evaporation heat transfer performance of porous surface","authors":"S. Hirasawa, T. Nakajima, Tetsuya Urimoto, Yuya Tsujimoto, Y. Takeuchi, T. Kawanami, K. Shirai","doi":"10.1109/ITHERM.2016.7517520","DOIUrl":"https://doi.org/10.1109/ITHERM.2016.7517520","url":null,"abstract":"Enhancement of evaporation heat transfer performance is important for cooling of electronic devices. Evaporation heat transfer coefficient of two types of porous surfaces supplied with water liquid film was studied experimentally. First porous surface was multi layers of meshed plates with micro-channel of 0.3 mm width. Thin water liquid film was supplied to the porous surface by bubbles. Evaporation heat transfer coefficient of the porous surface with one or two layers of meshed plates was 8×104 W/m2K and it was higher than pool boiling heat transfer coefficient. Second porous surface was 1 mm thickness of glass-beads of 0.4 mm in diameter on a heated cupper plate. Water was supplied to the porous layer at the center of the plate. Evaporation heat transfer coefficient was 1000 W/m2K after water was supplied. Evaporation heat transfer coefficient increased to 7000 W/m2K before appearance of dry portion on the plate, because water film thickness in the porous layer was thin.","PeriodicalId":426908,"journal":{"name":"2016 15th IEEE Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm)","volume":"24 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2016-07-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134340393","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2016-07-20DOI: 10.1109/ITHERM.2016.7517675
F. Faili, W. Huang, J. Calvo, Martin Kuball, D. Twitchen
With more phonons carrying the energy in the lattice, the phonon density of states in diamond extends to a much higher frequencies than that of any other material. This is related to the Debye temperature of diamond, being the highest of any bulk materials and of having the highest sound velocity of any known bulk materials. However, the thermal conductivity not only depends on the number of phonons and how fast they are, but also on how long they can travel without being disturbed or scattered. The measurement of this length of travel is the Mean Free Path of the phonons, l, which depends on the number of phonons in the lattice through the 3-phonon processes (Normal and Umpklapp), and the imperfections in the lattice (boundaries, grain boundaries, non sp3 bonds, isotopes, impurities, extended defects, dislocations, etc.). Consequently, the “real world” thermal conductivity of a given piece of diamond will depend on the “quality” of the lattice, yielding values from 1 W/m°K (ultra-nanocrystalline diamond) to more than 3400 W/m°K for isotopically pure single crystal diamond.
{"title":"Disturbed and scattered: The Path of thermal conduction through diamond lattice","authors":"F. Faili, W. Huang, J. Calvo, Martin Kuball, D. Twitchen","doi":"10.1109/ITHERM.2016.7517675","DOIUrl":"https://doi.org/10.1109/ITHERM.2016.7517675","url":null,"abstract":"With more phonons carrying the energy in the lattice, the phonon density of states in diamond extends to a much higher frequencies than that of any other material. This is related to the Debye temperature of diamond, being the highest of any bulk materials and of having the highest sound velocity of any known bulk materials. However, the thermal conductivity not only depends on the number of phonons and how fast they are, but also on how long they can travel without being disturbed or scattered. The measurement of this length of travel is the Mean Free Path of the phonons, l, which depends on the number of phonons in the lattice through the 3-phonon processes (Normal and Umpklapp), and the imperfections in the lattice (boundaries, grain boundaries, non sp3 bonds, isotopes, impurities, extended defects, dislocations, etc.). Consequently, the “real world” thermal conductivity of a given piece of diamond will depend on the “quality” of the lattice, yielding values from 1 W/m°K (ultra-nanocrystalline diamond) to more than 3400 W/m°K for isotopically pure single crystal diamond.","PeriodicalId":426908,"journal":{"name":"2016 15th IEEE Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm)","volume":"26 11-12","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2016-07-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132498114","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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