----------------------------------------------------- ISTANBUL FIZIK TAKVIMI; 17 Kasim 2008 Sayisi ----------------------------------------------------- LUTFEN DUYURU TAHTASINA ASINIZ ---------------------------------------------------- Sayın Meslektaşım, Nano-magnetizma ve spintronik konularındaki araştırmaları ve geliştirdiği teknoloji ile bilgisayar hafızalarının yüzlerce kat artmasına ve hızlanmasına katkısından ötürü 2007 yılı Nobel Ödülü alan Prof. Peter Grünberg, GYTE de kurmayi planladığımız ''NANO-Magnetizma ve Spintronik Araştırma Merkezi''nin planlarını değerlendirmek için 16-22 Kasım 2008 tarihleri arasında Enstitümüzü ziyaret edecektir. Prof. Peter Grünberg 17 Kasım (Pazartesi, saat 14:00) 2008 tarihinde "A short history of the electron: from amber to GMR" adlı bir de konferans verecektir. Teknolojinin bugünki seviyesine ulaşmasının ve bundan sonra göstereceği seyrin değerlendirimesinin yapılacağı bu ilginç konferansı onurlandırmanızı diler saygılarımı sunarım. Prof. Bekir AKTAŞ GYTE, Fizik Bölümü Başkanı Tel.0262 605 1301, GSM:0506 893 6485 e-mail:aktas@gyte.edu.tr Not: Katılacak kişilerin 12/11/2008 Tarihine kadar yer ayarlamamız için faik@gyte.edu.tr adresine mesaj gondermeleri işlerimizi kolaylaştıracaktır Prof. Bekir AKTAS Head of Physics Department, Gebze Institute of Technology, TURKEY ---------------------------------------------------- BILKENT UNIVERSITY PHYSICS DEPARTMENT SEMINAR SPINTRONICS WITH MOLECULAR STRUCTURES R. Tuğrul SENGER Bilkent Üniversitesi, Fizik Bölümü, 06800 Ankara Using molecular structures various spin-dependent effects can be utilized towards realization of next-generation spintronic devices. In this talk, molecular structures that break the spin symmetry of the electrons that contribute to the current through them will be considered. Emphasis will be given to short graphene nanoribbon (graphene flake) system where we show that a spin-polarized current can be induced without using magnetic entities or ferromagnetic electrodes. Ballistic conductance calculations based on density functional theory and Landauer-Büttiker formalism will be presented. Model systems of carbon atomic chains doped with transition-metal atoms and organometallic cobalt-benzene complexes will also be briefly discussed. Date: November 19, 2008 (Wednesday) Time: 15:40 Place: Faculty of Science Building A, Room 240 Tea and cookies will be served after the seminar. All interested are cordially invited. ---------------------------------------------------- Date: November 19, 2008, 15:30 (Tea & Cookies at 15:00) Place: Feza Gursey Seminar Room, Bogazici University, Physics Department Speaker: T. L. Kirk, Laboratory for Solid State Physics, ETH Zurich Title: Near Field Emission Scanning Electron Microscopy Abstract: In conventional scanning electron microscopy (SEM) the lateral resolution is limited by the electron beam diameter impinging on the specimen surface and interaction volume of the electron collisions. This limit is also critical for the subsequent analysis of the resultant electrons, e.g. spin polarization (SEMPA), electron energy loss spectroscopy (EELS), and auger electron spectroscopy (AES). The close proximity between the probe and sample surface of a scanning tunneling microscope (STM) operating in field emission (FE) mode provides a means of overcoming this limit. In this talk, I present a simple "near field emission scanning electron microscope" (NFESEM) capable of imaging conducting surfaces with high spatial resolution. This microscope is also refined to overcome the problems associated with the prior art, while introducing a means of comparative surface imaging using both the variations in electron intensity and the FE current. Variable current imaging generated by an STM operated in constant height (CH) mode has often been used to produce high resolution images of the surface. Moreover, STM FE mode operation was also used for mapping the FE sites on surfaces. It is our intention to employ such well-known imaging techniques as a comparison to our electron intensity images, which are the product of the primary beam of field-emitted electrons from an STM tip. I will report on the first topographic electron intensity image of terraces and mono-atomic steps on a single crystal substrate, not yet attained with a remote electron gun in conventional SEM. In addition the simultaneously recorded FE current surface mapping, limited only by the incident beam girth, closely resembles the topography of the electron intensity. This indicates that the maximum resolution, in accordance with the tip-sample geometry, has been reached. High spatial resolution was achieved by adhering to established theoretical models relating to the beam width of field-emitted electrons from a sharp Tungsten (W)-tip , which was shown to mainly depend on the emitter radius and the tip-sample separation gap. Complimentary STM imaging, directly following NFESEM measurements, is feasible and can easily be performed. We assert that additional analysis of the secondary electrons will also exhibit a comparable resolution. This is ongoing work in collaboration with Dr. Urs Ramsperger and Prof. Dr. Danilo Pescia. Contact: Muhittin Mungan, Bogazici University, Physics Department. (212) 359 6891 (o) mmungan@boun.edu.tr --------------------------------------------- TÜBİTAK-BOĞAZİÇİ UNIVERSITY FEZA GÜRSEY INSTITUTE KANDİLLİ-İSTANBUL SEMINAR Worldline formalism and it's application to AdS/CFT Correspondence 20 November 2008 THURSDAY (14:00) Shahin Mammadov Institute for Physical Problems Baku State University Abstract This talk consists in two brief lectures on introduction to worldline formalism and application of this formalism to AdS/CFT correspondence of current correlators. In first lecture we shall demonstrate how a formalism can be constructed on the basis of Schwinger's proper time parameter, which is named the worldline formalism and which is effectively applied to calculations of some loop diagrams in field theories. In second lecture it will be talked about Gopakumar's approach to bulk to boundary corresponding correlators of scalar current in AdS/CFT theory applying this formalism. Also will be shown possibility to extend this approach to AdS/CFT correspondence of R-current correlators. --------------------------------------------- TÜBİTAK-BOĞAZİÇİ UNIVERSITY-FEZA GÜRSEY INSTITUTE KANDİLLİ-İSTANBUL SEMINAR Block Copolymers at Surfaces: Self-Assembly, Templates, and Electric Fields 21 November 2008 FRIDAY (14:00) David ANDELMAN Tel Aviv University Abstract : Self-assembling domains in the nano scales are observed in a wide variety of physical and chemical systems. We will review the phenomenology behind these patterns and shapes as seen in block copolymers. We will discuss, in particular, several recent advances in thin films of block copolymers. Chemically patterned surfaces induce complex film morphology, while the substrate roughness affects the orientation of the copolymers. A second topic is the behavior of thin films in presence of external electric fields in the range of 1-100V/micron. Such fields can re-orientate phases of block copolymers and even cause morphological phase transitions. -------------------------------------------- İTÜ FEN-EDEBİYAT FAKÜLTESİ FİZİK BÖLÜMÜ SEMİNERİ Aktif Galaktik Çekirdeklerde Yıldız Parçalanması ile Oluşan Disklerin Evrimi K. Yavuz Ekşi İTÜ, Fizik Müh. Bölümü e-mail:eksi@itu.edu.tr Tüm aktif galaksilerin merkezinde etrafındaki bir diskten kütle aktarımı yapmakta olan ∼106-108 Güneş kütlesi’nde kara delikler olduğu düşünülmektedir. Kara deliğin yakınlarındaki bir yıldızı gel-git kuvvetleri ile parçalayarak böyle bir disk oluşturabileceği önerilmiş ve buna dair olduğu düşünülen gözlemsel parlama olayları kaydedilmiştir. Böyle bir diskin evrimi linear olmayan bir difüzyon denklemi ile belirlenmektedir. Bu çalışmada bu disklerin evrimi analitik ve nümerik olarak incelenecek, daha önce var olan analitik modeller geliştirilerek evrimin diskin başlangıç kütlesi ve açısal momentumu ile nasıl belirlendiği ortaya konacaktır. Gözlemsel parlama olayları modellenerek parçalanan yıldızın kütlesi ve açısal momentumu hakkında kestirimlerde bulunulacaktır. 21 Kasim 2008, Cuma Saat: 15:30 Yer: Fizik Bölümü Toplantı Salonu (İTÜ, Fen Edeb. Fak. Binası, Maslak Kampüsü) SAAT 15:30 DA ÇAY SERVİSİMİZ VARDIR --------------------------------------------- Sayın TUBA Konferansları İlgililerimiz Cumhuriyet Gazetesi Bilim ve politika yazarı Sayın Orhan Bursalı 24 Kasım 2008 Pazartesi günü saat 18:30'da TÜBA İstanbul Ofisinde (İTÜ Eski Maden Fakültesi, Yabancı Diller Yüksek Okulu, Maçka-İstanbul, Tel (0212 219 1660) Ana Değer Yaratıcı Olarak Bilgi Toplumu Sınıfı, Dünya ve iktidar Sorunu konulu bir konferans verecektir. Konferansa katılabilmeniz ricasıyla, en iyi dileklerimi sunarım. Prof Dr Namık Kemal Aras TÜBA İstanbul Akademi Forum Konferansları Yürütücüsü --------------------------------------------- Date: December 1, 2008, 15:30 (Tea & Cookies at 15:00) Place: Feza Gursey Seminar Room, Bogazici University, Physics Department Speaker: Ozhan Ozatay, Hitachi Global Storage Technologies, San Jose Research Center Title: 3D Solid State Memory: On The Road To Ultra-High Density Storage Abstract: Storing information in more and more compact ways, going well beyond what has been achieved in today's technology, is a great challenge. There are two mainstream approaches that are being pursued to push the technological limitations on data storage density; one is the semiconductor device approach, such as flash technology, where information is stored as charge trapped on a gate electrode, and the other one being the magnetic storage, such as hard drive technology, where information is stored as small magnetic domains on a continuous medium. Future improvements in the data storage density are limited in both technologies due to thermal stability issues in magnetic recording and charge leakage in flash memory devices making it very difficult to retain stored data for long periods of time. In this talk I will discuss the nanoscale physics of chalcogenide-based phase change memory devices and stacked magnetic nanowires developed to realize reliable data storage with ultra-high densities by utilizing the 3rd dimension. Dramatic and ultra-fast (nanosecond scale) changes in the physical properties such as electrical resistivity and optical reflectivity upon amorphization or crystallization makes chalcogenides ideal potential candidates for a universal non-volatile memory device, especially if, the device switching characteristics are highly scalable to nanometer dimensions. In the first part of my talk I will introduce a resistance mapping technique whereby we apply electrical pulses of various amplitudes, widths and trailing edges and deduce the resulting phase composition in nanoscale Ge2Sb2Te5 nanopillar devices. Such resistance map measurements provide a detailed picture of the scaling behaviour of the critical phase change conditions and the associated switching dynamics. A comparison of the observed characteristics with a three-dimensional finite element model (3D-FEM) of the electro-thermal physics enables a good assessment of the resulting device performance while providing physical insights into the nature of resistance switching behaviour. In the second part of my talk I will discuss an alternative, magnetic approach using stacks of magnetic nanowires to store and transfer magnetic bits. We use the localized stray field from a magnetic tip to write single-domains in a CoNi/Pd magnetic layer by modulating its coercivity via instantaneous and localized heating from a current pulse. Our studies have shown threshold current densities on the order of ~107 A/cm2 for 10 ns write times. I will present our detailed investigation of the resulting domain structure in nanowires with various widths as a function of the current pulse amplitude and width to vary the local temperature and the tip height to vary the local field. I will also discuss the nature of current-induced demagnetization limit and thermally-induced domain transfer between magnetic layers and compare the results with 3D finite element simulations of the thermal distribution profile. Contact: Muhittin Mungan, Bogazici University, Physics Department. (212) 359 6891 (o) mmungan@boun.edu.tr --------------------------------------------- Kıymetli Meslekdaşımız, 20-25 Ocak 2009 ve 26-28 Ocak 2009 tarihlerinde düzenlediğimiz Nanoelektronik ve Nanofotonik başlıklı Kış Okulu ve Çalıştay ile ilgili duyurular ektedir. Bilgilerinize arz ederiz. Organizasyon Komitesi adına, Atilla Aydınlı Profesör Fizik Bölümü Bilkent Üniversitesi 06800, Ankara Tel : (312) 290 1579 Belgeç: (312) 266 4579 Doç.Dr. Oğuz Gülseren Fizik Bölümü Bilkent Üniversitesi 06800, Ankara Tel : (312) 290 1937 Belgeç: (312) 266 4579 --------------------------------------------- ISTANBUL FIZIK TAKVIMI'nin ileriki sayisi icin, onumuzdeki haftalarda bolumunuzde olacak seminer ve benzer etkinlikler uzerine bilgileri, eger asagidaki takvime konmamislarsa, guclu@itu.edu.tr adresine yollamanizi rica ederim (lutfen yalniz e-mail mesaji olarak, attached document olarak degil). Bu bilgiler sunlari icerebilir: 1) Seminerin basligi, 2) Konusmaci, 3) Konusmacinin adresi, 4) mumkunse konusmanin ozeti 5) Seminerin saati, tarihi, yeri, yerinin adresi 6) Seminerle ilgili iletisim kurabilmek icin duzenleyen kisinin kim oldugu, telefonu ve elektronik adresi 7) Istanbul disindan bir konusmacinin Istanbul'da ne sure kalacagi ve kendisiyle ozel gorusme olanagi Takvimde belirtilecek konusmalar fizik ve fizikcilerin ilgilendigi diger fen ve muhendislik konularindadir. Konusmalarin ilani takvime MUMKUN OLDUGU KADAR ERKEN konup, konusmanin tarihine kadar Takvimde tekrar edilir. Dolayisiyla, bilgilerin kismen bile olsa - daha sonra tamamlanabilir - BELIRLENIR BELIRLENMEZ iletilmesi onemlidir. Seminerden birkac gun once iletilen bilgilerin Takvime girebilme olasiligi dusuktur. Takvim size bir veya iki haftada bir ulasacaktir. Takvimi kagida basip bolumunuzun duyuru tahtalarina asmaniz cok yararli olur. Takvimin dagitimina eklenmesi gereken meslekdaslarin elektronik adreslerini bildirmenizi, ote yandan eger takvimin size gonderilmesini istemiyorsaniz bildirmenizi rica ederim. Tesekkur eder ve iyi calismalar dilerim. -- Dr. M. Cem Guclu Istanbul Technical University Department of Physics Ayazaga Campus Maslak 80626 Istanbul Tel: 0(212) 285 3217 Fax: 0(212) 285 6386 e-mail : guclu@itu.edu.tr http://atlas.cc.itu.edu.tr/~guclu/