Surface segregation is studied via the evolution of reflection high-energy electron diffraction （RHEED） patterns under different values of As4 BEP for InGaAs films. When the As4 BEP is set to be zero, the RHEED patt...Surface segregation is studied via the evolution of reflection high-energy electron diffraction （RHEED） patterns under different values of As4 BEP for InGaAs films. When the As4 BEP is set to be zero, the RHEED pattern keeps a 4x3/（nx3） structure with increasing temperature, and surface segregation takes place until 470 ℃ The RHEED pattern develops into a metal-rich （4x2） structure as temperature increases to 495℃. The reason for this is that surface segregation makes the In inside the InGaAs film climb to its surface. With the temperature increasing up to 515℃, the RHEED pattern turns into a GaAs（2x4） structure due to In desorption. While the As4 BEP comes up to a specific value （1.33 x 10-4 Pa-1.33 x 10-3 Pa）, the surface temperature can delay the segregation and desorption. We find that As4 BEP has a big influence on surface desorption, while surface segregation is more strongly dependent on temperature than surface desorption.展开更多
This work presents an in-situ technique to quantify the layer-by-layer roughness of thin films and heterostructures by measuring the spectral profile of the reflection high-energy electron diffraction(RHEED).The chara...This work presents an in-situ technique to quantify the layer-by-layer roughness of thin films and heterostructures by measuring the spectral profile of the reflection high-energy electron diffraction(RHEED).The characteristic features of the diffraction spot,including the vertical to lateral size ratio c/b and the asymmetrical ratio c_(1)/c_(2) along the vertical direction,are found to be quantitatively dependent on the surface roughness.The quantitative relationships between them are established and discussed for different incident angles of high-energy electrons.As an example,the surface roughnesses of LaCoO_(3) films grown at different temperatures are obtained using such an in-situ technique,which are confirmed by the ex-situ atomic force microscopy.Moreover,the in-situ measured layer-by-layer roughness oscillations of two LaCoO_(3) films are demonstrated,revealing drastically different information from the intensity oscillations.The experiments assisted with the in-situ technique demonstrate an outstanding high resolution down to-0.1 A.Therefore,the new quantitative RHEED technique with real-time feedbacks significantly escalates the thin film synthesis efficiency,especially for achieving atomically smooth surfaces and interfaces.It opens up new prospects for future generations of thin film growth,such as the artificial intelligence-assisted thin film growth.展开更多
We established a model to simulate the growth process of nitridation and clarified the inner mechanisms ofnitridation and over-nitridation by combining the kinetic Monte Carlo and molecular dynamics methods. Supported...We established a model to simulate the growth process of nitridation and clarified the inner mechanisms ofnitridation and over-nitridation by combining the kinetic Monte Carlo and molecular dynamics methods. Supported by reflection high-energy electron diffraction results with growth in an MBE system, the tendency of nitridation on s-sapphire in different conditions was observed and analyzed. The best conditions for nitridation on the a-sapphire surface are found by our simulation.展开更多
基金supported by the National Natural Science Foundation of China (Grant No. 60866001)the Special Assistant to High-Level Personnel Research Projects of Guizhou Provincial Party Committee Organization Department of China (Grant No. TZJF- 2008-31)+3 种基金the Support Plan of New Century Excellent Talents of Ministry of Education, China (Grant No. NCET-08-0651)the Doctorate Foundation of the State Education Ministry of China (Grant No. 20105201110003)the Special Governor Fund of Outstanding Professionals in Science and Technology and Education of Guizhou Province, China (Grant No. 2009114)the Doctoral Foundation Projects of Guizhou College of Finance and Economics in 2010
文摘Surface segregation is studied via the evolution of reflection high-energy electron diffraction （RHEED） patterns under different values of As4 BEP for InGaAs films. When the As4 BEP is set to be zero, the RHEED pattern keeps a 4x3/（nx3） structure with increasing temperature, and surface segregation takes place until 470 ℃ The RHEED pattern develops into a metal-rich （4x2） structure as temperature increases to 495℃. The reason for this is that surface segregation makes the In inside the InGaAs film climb to its surface. With the temperature increasing up to 515℃, the RHEED pattern turns into a GaAs（2x4） structure due to In desorption. While the As4 BEP comes up to a specific value （1.33 x 10-4 Pa-1.33 x 10-3 Pa）, the surface temperature can delay the segregation and desorption. We find that As4 BEP has a big influence on surface desorption, while surface segregation is more strongly dependent on temperature than surface desorption.
基金supported by the National Science Foundation of China(No.52072244)the ShanghaiTech Startup Fund,and the Fundamental Research Funds for the Central Universities(No.WK2340000088).
文摘This work presents an in-situ technique to quantify the layer-by-layer roughness of thin films and heterostructures by measuring the spectral profile of the reflection high-energy electron diffraction(RHEED).The characteristic features of the diffraction spot,including the vertical to lateral size ratio c/b and the asymmetrical ratio c_(1)/c_(2) along the vertical direction,are found to be quantitatively dependent on the surface roughness.The quantitative relationships between them are established and discussed for different incident angles of high-energy electrons.As an example,the surface roughnesses of LaCoO_(3) films grown at different temperatures are obtained using such an in-situ technique,which are confirmed by the ex-situ atomic force microscopy.Moreover,the in-situ measured layer-by-layer roughness oscillations of two LaCoO_(3) films are demonstrated,revealing drastically different information from the intensity oscillations.The experiments assisted with the in-situ technique demonstrate an outstanding high resolution down to-0.1 A.Therefore,the new quantitative RHEED technique with real-time feedbacks significantly escalates the thin film synthesis efficiency,especially for achieving atomically smooth surfaces and interfaces.It opens up new prospects for future generations of thin film growth,such as the artificial intelligence-assisted thin film growth.
文摘We established a model to simulate the growth process of nitridation and clarified the inner mechanisms ofnitridation and over-nitridation by combining the kinetic Monte Carlo and molecular dynamics methods. Supported by reflection high-energy electron diffraction results with growth in an MBE system, the tendency of nitridation on s-sapphire in different conditions was observed and analyzed. The best conditions for nitridation on the a-sapphire surface are found by our simulation.
