Statistics and Probability Characteristics of Typical Surface Defects of Subway Tunnels

2022 ◽  
Vol 36 (1) ◽  
Author(s):  
Zhen Huang ◽  
Wei Zhang ◽  
Jiabing Zhang ◽  
Helin Fu ◽  
Wei Yang
Keyword(s):  
Surface Defects ◽  
Statistics And Probability ◽  
Subway Tunnels

Defects in Crystals

1968 ◽  
Vol 26 ◽  
pp. 244-245
Author(s):  
Kenneth R. Lawless
Keyword(s):  
Electron Microscope ◽  
Point Defects ◽  
Surface Defects ◽  
Chemical Properties ◽  
Material Point ◽  
Crystal Defects ◽  
Defects In Crystals ◽  
Irradiation Effects ◽  
Normal Lattice ◽  
Line Defects

One of the most important applications of the electron microscope in recent years has been to the observation of defects in crystals. Replica techniques have been widely utilized for many years for the observation of surface defects, but more recently the most striking use of the electron microscope has been for the direct observation of internal defects in crystals, utilizing the transmission of electrons through thin samples.Defects in crystals may be classified basically as point defects, line defects, and planar defects, all of which play an important role in determining the physical or chemical properties of a material. Point defects are of two types, either vacancies where individual atoms are missing from lattice sites, or interstitials where an atom is situated in between normal lattice sites. The so-called point defects most commonly observed are actually aggregates of either vacancies or interstitials. Details of crystal defects of this type are considered in the special session on “Irradiation Effects in Materials” and will not be considered in detail in this session.

Characterization of homoepitaxial diamond films by Electron microscopy

1991 ◽  
Vol 49 ◽  
pp. 880-881
Author(s):  
D.P. Malta ◽  
S.A. Willard ◽  
R.A. Rudder ◽  
G.C. Hudson ◽  
J.B. Posthill ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Surface Defects ◽  
Substrate Surface ◽  
Diamond Films ◽  
Chemical Vapor ◽  
Polycrystalline Diamond ◽  
Large Degree ◽  
Rf Plasma ◽  
Semiconducting Diamond

Semiconducting diamond films have the potential for use as a material in which to build active electronic devices capable of operating at high temperatures or in high radiation environments. A major goal of current device-related diamond research is to achieve a high quality epitaxial film on an inexpensive, readily available, non-native substrate. One step in the process of achieving this goal is understanding the nucleation and growth processes of diamond films on diamond substrates. Electron microscopy has already proven invaluable for assessing polycrystalline diamond films grown on nonnative surfaces.The quality of the grown diamond film depends on several factors, one of which is the quality of the diamond substrate. Substrates commercially available today have often been found to have scratched surfaces resulting from the polishing process (Fig. 1a). Electron beam-induced current (EBIC) imaging shows that electrically active sub-surface defects can be present to a large degree (Fig. 1c). Growth of homoepitaxial diamond films by rf plasma-enhanced chemical vapor deposition (PECVD) has been found to planarize the scratched substrate surface (Fig. 1b).

Microstructure of sputter deposited Ni-Sb ohmic contacts on GaAs

1989 ◽  
Vol 47 ◽  
pp. 450-451
Author(s):  
S. Yegnasubramanian ◽  
V.C. Kannan ◽  
R. Dutto ◽  
P.J. Sakach
Keyword(s):  
High Performance ◽  
Ohmic Contacts ◽  
Surface Defects ◽  
Pure Metal ◽  
Device Fabrication ◽  
Native Oxide ◽  
Metal Thin Films ◽  
Recent Developments ◽  
Different Temperatures ◽  
Sputter Deposited

Recent developments in the fabrication of high performance GaAs devices impose crucial requirements of low resistance ohmic contacts with excellent contact properties such as, thermal stability, contact resistivity, contact depth, Schottky barrier height etc. The nature of the interface plays an important role in the stability of the contacts due to problems associated with interdiffusion and compound formation at the interface during device fabrication. Contacts of pure metal thin films on GaAs are not desirable due to the presence of the native oxide and surface defects at the interface. Nickel has been used as a contact metal on GaAs and has been found to be reactive at low temperatures. Formation Of Ni2 GaAs at 200 - 350C is reported and is found to grow epitaxially on (001) and on (111) GaAs, but is shown to be unstable at 450C. This paper reports the investigations carried out to understand the microstructure, nature of the interface and composition of sputter deposited and annealed (at different temperatures) Ni-Sb ohmic contacts on GaAs by TEM. Attempts were made to correlate the electrical properties of the films such as the sheet resistance and contact resistance, with the microstructure. The observations are corroborated by Scanning Auger Microprobe (SAM) investigations.

Contrasts of planar defects in reflection electron microscopy

1993 ◽  
Vol 51 ◽  
pp. 1004-1005
Author(s):  
Feng Tsai ◽  
J. M. Cowley
Keyword(s):  
Electron Microscopy ◽  
Surface Defects ◽  
Practical Importance ◽  
Theoretical Treatment ◽  
Crystal Surfaces ◽  
Planar Defects ◽  
Surface Steps ◽  
Surface Reconstructions ◽  
Domain Boundaries ◽  
Reflection Electron Microscopy

Reflection electron microscopy (REM) has been used to study surface defects such as surface steps, dislocations emerging on crystal surfaces, and surface reconstructions. However, only a few REM studies have been reported about the planar defects emerging on surfaces. The interaction of planar defects with surfaces may be of considerable practical importance but so far there seems to be only one relatively simple theoretical treatment of the REM contrast and very little experimental evidence to support its predications. Recently, intersections of both 90° and 180° ferroelectric domain boundaries with BaTiO3 crystal surfaces have been investigated by Tsai and Cowley with REM.The REM observations of several planar defects, such as stacking faults and domain boundaries have been continued by the present authors. All REM observations are performed on a JEM-2000FX transmission electron microscope. The sample preparations may be seen somewhere else. In REM, the incident electron beam strikes the surface of a crystal with a small glancing angle.

Electron Channelling Contrast Imaging of Dislocations

1990 ◽  
Vol 48 (1) ◽  
pp. 600-601
Author(s):  
J.T. Czernuszka ◽  
N.J. Long ◽  
P.B. Hirsch
Keyword(s):  
Field Emission ◽  
Secondary Electron ◽  
Surface Defects ◽  
Spot Size ◽  
Beam Divergence ◽  
Contrast Imaging ◽  
Scattered Electron ◽  
Near Surface ◽  
Filter System ◽  
Electron Channelling

In the 1970s there was considerable interest in the development of the electron channelling contrast imaging (ECCI) technique for imaging near surface defects in bulk (electron opaque) specimens. The predictions of the theories were realised experimentally by Morin et al., who used a field emission gun (FEG) operating at 40-50kV and an energy filter such that only electrons which had lost no more than a few 100V were detected. This paper presents the results of a set of preliminary experiments which show that an energy filter system is unneccessary to image and characterise the Burgers vectors of dislocations in bulk specimens. The examples in the paper indicatethe general versatility of the technique.A VG HB501 STEM with a FEG was operated at 100kV. A single tilt cartridge was used in the reflection position of the microscope. A retractable back-scattered electron detector was fitted into the secondary electron port and positioned to within a few millimetres of the specimen. The image was acquired using a Synoptics Synergy framestore and digital scan generator and subsequently processed using Semper 6. The beam divergence with the specimen in this position was 2.5 mrads with a spot size of approximately 4nm. Electron channelling patterns were used to orientate the sample.

Studies of Ge/Si(100) and Observation of Atomic Steps on Si(100) using Biassed Secondary Electron Imaging in a UHV STEM

1990 ◽  
Vol 48 (1) ◽  
pp. 308-309
Author(s):  
Mohan Krishnamurthy ◽  
Jeff S. Drucker ◽  
John A. Venablest
Keyword(s):  
Secondary Electron ◽  
Critical Thickness ◽  
Surface Defects ◽  
Film Growth ◽  
Growth Parameters ◽  
High Vacuum ◽  
Ultra High Vacuum ◽  
Surface Steps ◽  
Epitaxial Crystal Growth ◽  
Electron Imaging

Secondary Electron Imaging (SEI) has become a useful mode of studying surfaces in SEM[1] and STEM[2,3] instruments. Samples have been biassed (b-SEI) to provide increased sensitivity to topographic and thin film deposits in ultra high vacuum (UHV)-SEM[1,4]; but this has not generally been done in previous STEM studies. The recently developed UHV-STEM ( codenamed MIDAS) at ASU has efficient collection of secondary electrons using a 'parallelizer' and full sample preparation system[5]. Here we report in-situ deposition and annealing studies on the Ge/Si(100) epitaxial system, and the observation of surface steps on vicinal Si(100) using b-SEI under UHV conditions in MIDAS.Epitaxial crystal growth has previously been studied using SEM and SAM based experiments [4]. The influence of surface defects such as steps on epitaxial growth requires study with high spatial resolution, which we report for the Ge/Si(100) system. Ge grows on Si(100) in the Stranski-Krastonov growth mode wherein it forms pseudomorphic layers for the first 3-4 ML (critical thickness) and beyond which it clusters into islands[6]. In the present experiment, Ge was deposited onto clean Si(100) substrates misoriented 1° and 5° toward <110>. This was done using a mini MBE Knudsen cell at base pressure ~ 5×10-11 mbar and at typical rates of 0.1ML/min (1ML =0.14nm). Depositions just above the critical thickness were done for substrates kept at room temperature, 375°C and 525°C. The R T deposits were annealed at 375°C and 525°C for various times. Detailed studies were done of the initial stages of clustering into very fine (∼1nm) Ge islands and their subsequent coarsening and facetting with longer anneals. From the particle size distributions as a function of time and temperature, useful film growth parameters have been obtained. Fig. 1 shows a b-SE image of Ge island size distribution for a R T deposit and anneal at 525°C. Fig.2(a) shows the distribution for a deposition at 375°C and Fig.2(b) shows at a higher magnification a large facetted island of Ge. Fig.3 shows a distribution of very fine islands from a 525°C deposition. A strong contrast is obtained from these islands which are at most a few ML thick and mottled structure can be seen in the background between the islands, especially in Fig.2(a) and Fig.3.

Pengembangan Perangkat Pembelajaran Matematika Model Pembelajaran Berbasis Masalah untuk Meningkatkan Kualitas Proses dan Hasil Belajar di SMP

2019 ◽  
Vol 2 (2) ◽  
Author(s):  
Rini Dian Anggraini ◽  
Titi Solfitri
Keyword(s):  
High School ◽  
Small Group ◽  
Junior High School ◽  
Junior High ◽  
Lesson Plan ◽  
Mathematics Learning ◽  
Research Use ◽  
Large Group ◽  
Statistics And Probability ◽  
Group Trial

Penelitian ini bertujuan untuk mengembangkan perangkat pembelajaran matematika untuk sekolah menengah pertama yaitu kurikulum Silabus, Rencana Pembelajaran dan Lembar Kerja Siswa 2013 tentang statistik dan probabilitas dengan menggunakan model pembelajaran berbasis masalah. Penelitian ini menggunakan model pengembangan oleh Borg dan Gall yang dimodifikasi oleh Sugiyono (2008) melalui langkah-langkah: (1) potensi dan masalah; (2) pengumpulan data; (3) desain produk; (4) validasi desain; (5) revisi desain; (6) uji coba kelompok kecil; (7) revisi produk; (8) uji coba kelompok besar; (9) revisi produk. Pada tahap potensi dan masalah, para peneliti melakukan analisis potensi dan masalah. Kemudian, peneliti mengumpulkan data yang diperlukan sebagai referensi untuk desain perangkat pembelajaran matematika yang akan dikembangkan. Desain perangkat pembelajaran yang telah dikembangkan kemudian divalidasi oleh tiga validator dan direvisi berdasarkan saran validator. Hasil perancangan perangkat pembelajaran kemudian diujicobakan dalam uji coba kelompok kecil yang subjeknya 8 siswa kelas VII SMP Negeri 23 Pekanbaru. Setelah dicoba dalam uji coba kelompok kecil, kemudian direvisi berdasarkan kuesioner dari siswa yang mengikuti uji coba kelompok kecil. Setelah itu, para peneliti melakukan uji coba dalam kelompok besar yang subjeknya adalah 39 siswa kelas VII SMP Negeri 23 Pekanbaru, direvisi lagi dan disempurnakan. Berdasarkan hasil analisis dan diskusi data, perangkat pembelajaran yang telah dikembangkan valid yang nilai untuk Silabus adalah 3,39, rata-rata nilai untuk 5 Rencana Pelajaran adalah 3,41. Nilai rata-rata untuk 5 Lembar Kerja Siswa adalah 3,34. Lembar Kerja Siswa yang telah dikembangkan adalah persyaratan praktis yang memenuhi syarat untuk digunakan oleh siswa sekolah menengah pertama.   This research aimed to develop mathematics learning device for junior high school that are Syllabus, Lesson Plan and Students Worksheet curriculum 2013 on statistics and probability by used problem based learning model. This research use development model by Borg and Gall modified by Sugiyono (2008) through the steps : (1) potentials and problems; (2) data collection; (3) design product; (4) validation of design; (5) revision of design; (6) small group trial; (7) revision of product; (8) large group trial; (9) revision of product. At potentials and problems stage, the researchers conducted analysis of potentials and problems. Then, researchers collect the necessary data as reference to design of mathematics learning device that will be developed. Design of learning device that had been developed then validated by three validators and revised based on validator suggestion. The result of learning device design and then try out in small group trial which subjects are 8 students of VII SMP Negeri 23 Pekanbaru. After try out in small group trial, then it revised based on questionnaire from the students who take the small group trial. After that, the researchers conducted try out in large group trial which subjects are 39 students of VII SMP Negeri 23 Pekanbaru, revised again and refined. Based on result of data analysis and discussion, learning device that had been developed is valid which value for Syllabus is 3,39, the average of value for 5 Lesson Plan are 3,41. The average of value for 5 Students Worksheet are 3,34. Students Worksheet that had been developed is qualify practical requirement to used by students of junior high school.

Research on brake pad surface defects detection based on deep learning

2020 ◽  
Author(s):  
Tao Zhang ◽  
Yuting Liu ◽  
Yaning Yang ◽  
Yinggu Jin
Keyword(s):  
Deep Learning ◽  
Surface Defects ◽  
Brake Pad
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