The New TEM facility at LCI, KSU Min Gao Liquid Crystal Institute Kent State University 1 Questions to be answered • How does TEM work? • Why thin specimen? How to prepare one? • What is the TEM at LCI like? Functions available and principles? • How is the facility running so far? Any exciting results? • How to use the TEM lab? 2 Facts about the TEM facility at LCI Instruments Specifications Applications 3 What we have at LCI • FEI Tecnai F20ST-STEM – – – – – Schottky field mission gun 40 kV-200 kV 0.24 nm point-to-point resolution ±70° tilting angle 0.2 nm spot size • Attachments – Low-dose mode & tomography – EDAX energy dispersive x-ray spectrometer (EDS) – Gatan imaging filter (incl. EELS) – 4k*4K slow scan CCD – Cryo-holder & anti-contaminator • Assisting equipments – Vitrobot – Plasma cleaner – Vacuum station 4 How good is this microscope? “It would be very easy to make an analysis of any complicated chemical substance; all one would have to do would be to look at it and see where the atoms are. … I put this out as a challenge: Is there no way to make the electron microscope more powerful?” – Richard P. Feynman, 1959, “There’s Plenty of Room at the Bottom” Corrected EM in situ Haider (200keV) 1 Dietrich (200keV) 0.1 Electron Microscope -1 Resolution (Ang.) La in γ-Al2O3 Marton 0.01 Borisevich, 2004 0.001 Light Microscope Ruska Abbe 0.0001 Amici Ross 1800 1840 1880 1920 1960 2000 2040 Year Batson et al. Nature 2002 • Second best thing after corrected TEM • It is the best thing considering • Cost of TEM and maintenance • Easy to use • 85% applications do not need Cs corrector 5 General description of the TEM facility at LCI • Things making this facility standing out: the optimum integration of some most advanced TEM techniques, for example: cryoEM • An application-oriented versatile microscope • Excellent for materials science/life science/solid state physics/chemistry • Current setup: nanomaterials/soft-materials requiring simple sample preparation • A heavily computerized TEM with some bugseasy to operate 6 Philips and FEI microscopes EM420 CM200 7 “I've gotta see some atoms, excuse me,“ --Obama Titan 8 How much a TEM cost? • $4-5 per eV • 200 keV: 1M$ + accessories (easily up to 0.51M) extremely stable high-voltage supplies, extremely stable currents to each electromagnetic coil/lens, continuously-pumped high- or ultra-high-vacuum systems, and a cooling water supply circulation through the lenses and pumps. As they are very sensitive to vibration and external magnetic fields, microscopes designed to achieve high resolutions must be housed in stable buildings (sometimes underground) with special services such as magnetic field cancelling systems. There must be some solid reasons that we need such an expensive machine! 9 How does TEM work? Importance of thin specimens Electron-material interaction Techniques and Information 10 Advantage of thin samples 50 nm Cu, 25 kV, 5 nm probe, 1000 electrons Thin specimen in SEM 50 nm Cu, 200 kV, 1 nm probe, 1000 electrons (Thin specimen in) TEM Where is my surface? Surface damage 11 What thin samples do you need? • Represent the material you are studying: sometimes the thicker the better • Electron transparent: dependent on the accelerating voltage, thickness of the specimen, and atomic number of the specimen. • Uniformly thin • Stable under the electron beam • Conducing and nonmagnetic in the laboratory environment Generally speaking: 50-100 nm for conventional TEM; 15 nm for high resolution TEM 12 How to put the thin samples into the TEM? • The general form of a TEM specimen is a 3mm thin disk Supporting grids • Put the thin disk into a holder which goes to the TEM sample stage 13 How to prepare a thin sample? • Bulk materials: Agate Mortar and Pestle • Bulk & thin films: Wheel Saw Polishing machine Ion milling Dimpler A lot of techniques have been developed to make TEM specimens 14 Focused ion beam: TEM samples Au+Pd coating first Deposition of Pt protection layer Start of cutting View from 52° Under cut Other materials Nanomaterials: Biomaterials • Very easy • Quite difficult • Dispersed on supporting carbon film • Vitrobot • Ultramicrotomy 16 Electron-thin specimen interaction Cathodoluminescence Incident electron beam (E) Backscattered Electrons (Rutherford) Characteristic Xrays EDS Ef Ef Ef E E Secondary electrons Light Auger electrons Ef e-h pair EBIC Specimen Large-angle Incoherent elastically scattered electrons (Rutherford) Z-contrast STEM E-E Coherent elastically scattered electrons Diffraction Imaging HRTEM Inelastically scattered electrons Other signals from interaction with many nuclei or electrons: Bremsstrahlung x-ray (EDS), Plasma excitation (EELS) … EELS EFTEM 17 Instruments (TEM & STEM) Reimer, TEM, 1984 18 Information from a modern TEM Gao et al. PRB, 62, 5413 (2000) Gao et al. Unpublished In situ Why TEM? Gao et al. APL, 72, 2544 (1998) CBED Gao et al. JAP, 80, 4767 (1996) Gao et al. Z. Metallkd. 93, 438 (2002) EELS /EDS Gao et al. PRB, 62, 5413 (2000) O-K 1s 2p O Si Mo Mo/SiOx Si Gao & Duan, Mater. Trans. JIM, 39, 883, 1998 19 Knowing the limitations of TEM • Artifacts due to 2-D projections (3D TEM) • Interpretation of images • Poor Sampling: all TEMs have only examined <1 mm3 of materials! (First use low resolution but better sampling tools) • Electron beam irradiation and contamination (diffraction imaging, low temperature, low dose, cryoEM) • Sample preparation (low temperature, low-energy low angle ion milling, FIB-site specific, freeze-fracture, vitreous ethane ice) • Vacuum environment (environmental EM, in vitro) • Not so much about properties (in situ, combination) 20 Au+Si+O Si_L C_K O_K What have been done in the test running period at LCI? Service summary Available techniques Representative results 21 Number of samples FEI Cryo Training Min in China Cryo-trial Holiday TEM Startup Service hours Weekly service hours and number of samples Week Total service hours: 186 Cryo: 83 hrs Total number of samples: 113 Service hours vs groups Soumitra BasuTeaching Laurie Broadwater 6%1% 4% Songping Huang Mieteck Jaroniec 20% 20% 4% 8% L.C. Chen Peter Palffy-Muhoray 4% 3% 30% Quan Li Oleg Lavrentovich Tony Jakli Available TEM techniques • Imaging (diffraction contract, high resolution, Z-contrast, energy-filtered) • Diffraction (select-area, convergent beam, large angle CBED, nano-area) • Spectrometry (EDS, EELS) • CryoEM • 3D tomography • … 24 Imaging (contrast) • Mass and thickness contrast • Diffraction contrast • Phase contrast (e.g., HRTEM) • Z-contrast 25 Imaging (LCI) TEM bright field image and STEM Z-contrast (dark field) image Sample from Prof. Peter Palffy-Muhoray’s group HRTEM Sample from Prof. Peter PalffyMuhoray’s group HRTEM of quantum dots Sample from Prof. LC Chien’s group Diffraction Sample from Dr. Quan Li’s group 30 An interesting sample C SiOx Au Sample from Prof. Peter Palffy-Muhoray’s group EDS spectral imaging O Au Si Au+Si+O Si_L C_K O_K Sample from Prof. Peter Palffy-Muhoray’s group Cryo-Vitrobot – Controlled environment: temperature (4-60°C) and humidity (room cond. – 100%) – designed for bio and liquid – A small droplet of liquid is applied to pre-treated carbon film – Two filter papers are used to blot the liquid and leave a thin layer of liquid (e.g., 100 nm thick, adjustable blot force, time and repetition). – Shoot the sample into coolant (ethane) and freeze it at very high speed. First bio-sample Laurie Broadwater, Chemistry A thermotropic sample Sample from Prof. LC Chien’s group A lyotropic sample Sample from Prof. Oleg Lavrentovich’s group • Resolution beyond freeze fracture • Very challenging: <10 e/nm2 Sample from Prof. Jakli’s group Diffraction in Liquid Crystals Larger area Sample from Prof. Jakli’s group 3D tomography • A video taken by Dr. Lee Pullan (FEI) during the cryoEM training 39 Plan for the next step • Soon be running regularly – Rules and operation procedures – Usage rates (machine use, staff service) and billing –… • Self-user Training: – Single operator MG + several self-users – Right now: 1-on-1 based on research needs – Later: a TEM course including lab training if allowed • Web page of the facility 40 How to use the facility more efficiently • Highly efficient, professional, yet friendly service • The TEM will be aligned by the staff routinely, so you do not need to be an expert in TEM • Know your sample as well as possible • If you don’t know TEM so well, have an in-depth discussion with the staff before scheduling your experiment • Have a student with good experimental skills and a lot of patience • Analyze your data immediately • Introduce more outside users to keep the rates low • Acknowledge the facility properly • Pay your bill in time • … 41 Questions being answered • How does TEM work? • Why thin specimen? How to prepare one? • What is the TEM at LCI like? Functions available and principles? • How is the facility running so far? Any exciting results? • How to use the TEM lab? mgao@kent.edu 42