Study of Mos2 and Graphene-Based Heterojunctions for Electronic and Sensing Applications

Since the discovery of graphene, there has been an increase in two-dimensional (2D) materials research for their scalability down to atomic dimensions. Among the analogs of graphene, transition metal dichalcogenides (TMDs) are attractive due to their exceptional electronic and optoelectronic properties. MoS2, a TMD, has several advantages over graphene and the industry workhorse Si, and has been reported to demonstrate excellent transistor performances. The key obstacle in the commercialization of MoS2 technology is low carrier mobility over large areas for top-down devices. Although there were several early reports on synthesis of atomically thin MoS2 with moderate mobility, transferring large area grown films to a substrate of choice leads to interface charges that degrade mobility. In our work, a top-down growth technique for synthesizing large area, 3-5 monolayers (ML) thick MoS2 film have been presented by pre-oxidation of metallic Mo instead of direct sulfidation. The growth temperature was significantly reduced in this method, eliminating free sulfur-induced degradation of the SiO2 gate dielectric. As a result, the leakage current was suppressed by a factor of \u3e108, when compared to a single step direct sulfidation method. Using these thin films, back-gated field effect transistors have been demonstrated with accumulation electron mobility \u3e80 cm2/Vs, on/off \u3e105, and subthreshold swing of 84 mV/dec; which are among the best results for MoS2 based transistors on SiO2 substrate. A hypothesis on current saturation has also been presented, attributing it to charge control rather than velocity saturation. The second part of our work aims at utilizing the best properties both graphene and MoS2 simultaneously by forming a heterojunction of these two atomically thin materials. Interestingly, these two materials have certain contrasting properties, for example, graphene based FETs have poor switching performance while MoS2 based FETs can outperform many state-of-the-art ultra-low power transistors. Fabricating a Schottky diode made of graphene and MoS2 allows the unique properties of these two materials to be combined and has been shown to be useful. A key property of these 2D heterojunctions is that each constituent of the heterojunction is so thin that it may not be able to completely screen an electric field from the second constituent, i.e. the Debye screening length can be greater than the layer thicknesses, so that voltage-induced interfacial tuning is achievable. This capability is unique to thin layers, most practically achieved in 2D heterojunctions, and has been exploited in recent “barristors”, which are 3-terminal devices with Schottky diodes where the barrier height can be tuned by an insulated gate. Such a tunable Schottky diode, similar to a triode vacuum tube is attractive for applications in RF circuits, photodetection and chemical sensing, analog and digital electronics, etc, with all the advantages of solid state devices e.g. high speed, low-cost and compactness. In this work, a graphene/MoS2 heterojunction on SiO2 dielectric has been fabricated to demonstrate a functional barristor device. By varying the gate bias between -20 V and +10 V, the barrier height could be modulated by \u3e0.65 eV, potentially enabling current control over 10 orders of magnitude at room temperature. Using the current-voltage (I-V) and capacitance-voltage (C-V) characteristics of this device, we have also extracted the Richardson’s coefficient and electronic effective mass in MoS2 using a thermionic emission model, which are very important parameters required for proper engineering of these devices. After that, various applications of the barristor device have also been explored. The high optical response of the barristor has demonstrated the presence of photoconductive gain, and has been consistent with the changes in Schottky barrier height caused by the back-gate. The barristor has also been successful as gate-tunable toxic gas sensors, with lowest level detection lying around 100 ppb (parts per billion) for NO2 and 1 ppm (parts per million) for NH3. These observations highlight the potential applications of the graphene/MoS2 barristor for various electronic, optoelectronic and sensing applications. Finally, a mixed dimensional barristor made of graphene/InN nanowire heterojunction with a backgate has been demonstrated. The surface passivation of InN and the tunnel barrier formation at the graphene/NW interface have been achieved through controlled O2 plasma exposure, which has allowed an otherwise ohmic contact to turn into a gate tunable Schottky junction with \u3e1 eV barrier height. This device has been demostrated to perform sub-ppb level trace gas detection, photo-detection with very high sensitivity and a novel gate-controllable memristive action through longer O2 plasma exposure

MENINGKATKAN KEMAMPUAN MENGENAL BENTUK GEOMETRI MELALUI PERMAINAN KOTAK SORTASI PADA ANAK USIA 5 - 6 TAHUN

The Introduction of geometric shapes as one of mathematics learning in children needs to be improved from the earliest levels of education. This is motivated by the existence of some children who have difficulty learning to recognize geometric shapes. This study aims to determine the increase in the ability to recognize geometric shapes of children aged 5-6 years through the sorting box game. Sorting boxes make it easier for children to use them and learn one by one geometric shapes with attractive shapes and color designs. This study uses the Classroom Action Research method with the Kemmis and McTaggart models consisting of several cycles. Each cycle consists of plans, actions, observation, and reflection. Data collection techniques in the form of observation, interviews, and reflections. Data collection techniques in the form of observation, interviews, and documentation. Analysis of the data used is descriptive quantitative. This study involved 10 Kober Tunas Bangsa Sumedang District children, with 4 boys and 6 girls. The success of this research is if the child is able to draw shapes according to instructions, and shows, mentions, groups and arranges geometric shapes based on size and color. Evaluation of the results of the pre-cycle shows of children’s understanding of geometric shapes by 30%. In the first cycle, the increase reached 50%. While in cycle II, the increase in children’s success reached 80%. Thus, the sorting box game can improve the ability to recognize geometric shapes of children aged 5-6 years.Pengenalan bentuk geometri sebagai salah satu pembelajaran matematika pada anak perlu ditingkatkan dari mulai jenjang pendidikan yang paling dini. Hal ini dilatarbelakangi oleh adanya sebagian anak yang  mengalami kesulitan dalam belajar mengenal bentuk geometri. Penelitian ini bertujuan untuk mengetahui peningkatan kemampuan mengenal bentuk geometri anak usia 5-6 tahun melalui permainan kotak sortasi. Kotak sortasi mempermudah anak dalam menggunakannya dan mempelajari satu persatu bentuk geometri dengan desain bentuk dan warna menarik. Penelitian ini menggunakan metode Penelitian Tindakan Kelas dengan model Kemmis dan McTaggart yang terdiri dari beberapa siklus. Setiap siklus terdiri dari tahap rencana, tindakan, observasi dan refleksi. Teknik pengumpulan datanya berupa observasi, wawancara, dan dokumentasi. Analisis data yang digunakan yaitu deskriptif kuantitatif . Penelitian ini melibatkan 10 orang anak Kober Tunas Bangsa Kabupaten Sumedang, dengan 4 orang laki-laki dan 6 orang perempuan. Keberhasilan penelitian ini  apabila anak mampu menggambar bentuk sesuai perintah, serta menunjukkan, menyebutkan, mengelompokkan, dan menyusun bentuk geometri berdasarkan ukuran dan warna. Evaluasi hasil dari pra siklus menunjukkan pemahaman anak mengenal bentuk geometri sebesar 30%. Pada siklus I peningkatan mencapai 50%. Sementara pada siklus II, peningkatan keberhasilan anak mencapai 80%. Dengan demikian, permainan kotak sortasi dapat meningkatkan kemampuan mengenal bentuk geometri anak usia 5-6 tahun

Interactive or Uninteractive: How is the Implementation of English Song Improve Listening Skill Students at Junior High School? Interaktif atau Tidak Interaktif: Bagaimana Penerapan Lagu Bahasa Inggris Meningkatkan Keterampilan Mendengarkan Siswa di Sekolah Menengah Pertama?

For students, learning English can become monotonous and boring if most teachers continue to base their learning on reading from books. The importance of implementing listening learning in learning English in the classroom. This research was conducted using qualitative methods, the purpose of this study was to provide data that does not require quantification, so that the results are given in the form of a description based on the results obtained during the research. This study describes the application of songs, to improve students' listening skills in learning English in junior high schools. The research findings found that the difficulties faced by teachers in teaching listening were that not all students had favorite songs. Therefore, English teachers can provide a balanced portion of teaching listening skills as is the case with other language skills. Teaching listening skills is no longer a neglected skill.&nbsp

MENGEMBANGKAN KECERDASAN LINGUISTIK ANAK USIA DINI MELALUI METODE BERNYANYI

The intelligence that must exist in children is linguistic, linguistic intelligence is a person's ability to process or express words, writing, expressing thoughts, desires, and opinions. The purpose of this research is to develop linguistic intelligence in early childhood through the singing method. The method in this research is descriptive and qualitative. Data collection techniques in this study are observation, documentation, and interviews. The subjects in this study were children aged 4-5 years as many as 6 children and 2 teachers, school principals, and parents as informants. The instruments or methods of data collection in this study were observation, interviews, and relevant documentation. Data processing was carried out using qualitative data analysis, namely data reduction, data presentation, conclusion drawing, and verification according to the flow model. The use of qualitative descriptive research in this study is intended for the assessment technique obtained by collecting the results of observations, assessment results, and evaluations of children through developing linguistic intelligence for early childhood through the singing method. The results obtained that the level of children's linguistic achievement through the singing method developed very well and increased, from 6 children studied 5 children developed very well (BSB) in the four indicators studied while 1 child in the last indicator showed development as expected (BSH), this is has proven that there is a positive response from children in the implementation of the singing method.Kecerdasan yang harus ada pada anak adalah kecerdasan linguistik, kecerdasan linguistik adalah kemampuan seseorang untuk mengolah atau mengekspresikan kata-kata, tulisan, ungkapan pikiran keinginan dan pendapat. Tujuan dalam penelitian ini untuk mengembangkan kecerdasan linguistikanak usia dini melalui metode bernyanyi. Metode dalam penelitian ini adalah deskriptif kualitatif. Teknik pengumpulan data dalam penelitian ini yaitu observasi, dokumentasi dan wawancara. Subjek dalam penelitian ini anak usia 4-5 tahun sebanyak 6 anak dan 2 orang guru, kepala Sekolah serta orang tua sebagai informan. Instrumen atau metode pengumpulan data dalam penelitian ini adalah observasi, wawancara dan dokumentasi yang relevan. Pengolahan data yang dilakukan menggunakan analisis data kualitatif yaitu reduksi data, penyajian data, penarikan kesimpulan dan verifikasi sesuai model alir .Penggunaan penelitian deskriptif kualitatif dalam penelitian ini dimaksudkan untuk Teknik penilaian didapatkan dengan mengumpulkan hasil observasi, hasil penilaian dan evaluasi terhadap anak melalui mengembangkan kecerdasan linguistikanak usia dini melalui metode bernyanyi. Diperoleh hasil tingkat pencapaian linguistikanak melalui metode bernyanyi tersebut berkembang sangat baik dan meningkat, dari 6 anak yang diteliti 5 anak berkembang sangat baik (BSB) dalam empat indikator yang diteliti sedangkan 1 anak dalam indikator terakhir menunjukkan berkembang sesuai harapan (BSH), hal ini sudah membuktikan adanya respon positif dari anak dalam pelaksanaan metode bernyanyi tersebut.Â

MENINGKATKAN KECERDASAN LOGIKA MATEMATIKA MELALUI MODEL PEMBELAJARAN EXPERIANTIAL LEARNING

Efforts to develop mathematical intelligence in early childhood are needed, besides, to preparing children's social and emotional mental readiness, mathematical logic intelligence as a basis for developing mathematical abilities for readiness to attend basic education. Most of the children have not developed intelligence in mathematical logic, because learning is applied more often using textbooks, the teacher's competence in understanding the potential of children's intelligence is not fully understood, so children are less enthusiastic when learning. The purpose of this study was to determine the application of experiential learning models to improve the intelligence of mathematical logic in children aged 4-5 years. The method used was classroom action research with group A children (4-5 years old). consists of 11 girls and 11 boys in RA Multazam. The data collection techniques used are observation and documentation, the steps being carried out are initial observation, pre-cycle, cycle 1, cycle II, consisting of planning, action, observation, and reflection. Data analysis techniques used by reducing data, displaying data, and drawing conclusions. After being given action in the first cycle through experiential learning, there is a better chance, 4.5% of children begin to develop, 63% develop as expected, 31.8% of children develop very well. Based on the results of the study it can be concluded that through the experiential learning model learning can improve children's mathematical logic intelligence.Upaya pengembangan kecerdasan logika matematika anak usia dini sangat diperlukan, selain menyiapkan kesiapan mental sosial dan emosional anak, kecerdasan logika matematika sebagai dasar pengembangan kemampuan matematika untuk kesiapan mengikuti pendidikan dasar. Sebagian besar anak belum berkembang dalam  kecerdasan logika matematika, dikarenakan pembelajaran yang diterapkan  jarang menggunakan media,sehingga anak kurang antusias saat belajar. Tujuan dari penelitian ini untuk mengetahui penerapan model pembelajaran experiantial learning untuk meningkatkan kecerdasan logika matematika anak usia 4-5 tahun. Metode yang digunakan adalah Penelitian tindakan kelas (classroom action research) subjeknya anak kelompok A (4-5 tahun) terdiri dari11anak perempuan dan 11 anak laki-laki di RA Multazam. Teknik pengumpulan data yang digunakan adalah observasi dan dokumentasi, tahapan yang dilakukan yaitu observasi awal, pra siklus, siklus 1, siklus II, terdiri dari perencanaan, tindakan, observasi serta refleksi. Teknik analisis data yang digunakan dengan cara mereduksi data, mendisplay data, serta pengambilan kesimpulan. Setelah diberikan tindakan pada siklus I1 melalui pembelajaran experiantial learning maka ada perubahan yang lebih baik, 4,5% anak mulai berkembang, 63% berkembang sesuai harapan, 31,8% anak yang berkembang sangat baik. Berdasarkan hasil penelitian dapat disimpulkan bahwa melalui model pembelajaran experiantial learning dapat meningkatkan kecerdasan logika matematika anak