amber…greek name for amber was ἤ λεκτρον (elektron), “formed by the sun” around...
TRANSCRIPT
Amber…Greek name for amber was ἤλεκτρον (elektron), “formed by the sun”
Around 600bc, the Greek philosopher and scientist Thales of Miletus discovered that rubbing amber with a wool cloth would cause it to mysteriously attract paper, grass or feathers.
Electricity!
We learned shocking power (and something about forces of nature) from lightning…and fish!
Electricity!
We learned shocking power (and something about forces of nature) from lightning…and fish!
Electric catfish (Malapterurus electricus) 350V
Electric “eel” (Electrophorus electricus) 600V
Electric rays (~60 species) 40-50V
Elektron, the Greek word for amber…
William Gilbert (1600) is the first to recognize the difference between the magnetic attraction of magnetite, and the static charge attraction built up on the surface of amber after it is rubbed…
Ben Franklin
“electricus”
1752, lightning =static charge
1755, charge exists on the exterior of a charged object…the interior is unaffected (the cage effect)
George Johnstone Stoney
G. Johnstone Stoney in Aug. 1874, and again in Feb. 1881."And, finally, Nature presents us, in the phenomenon of electrolysis, with a single definite quantity of electricity which is independent of the particular bodies acted on. To make this clear I shall express `Faraday's Law' in the following terms, which, as I shall show, will give it precision, viz.:-- For each chemical bond which is ruptured within an electrolyte a certain quantity of electricity traverses the electrolyte which is the same in all cases. This definite quantity of electricity I shall call Er. If we make this our unit quantity of electricity, we shall probably have made a very important step in our study of molecular phenomena."
1891“In this paper an estimate was made of the actual amount of this most remarkable fundamental unit of electricity, for which I have since ventured to suggest the name electron. According to this determination the electron = a twentiethot (that is 10¯20) of the quantity of electricity which was at that time called the ampere…”
John Dalton (1766-1844)-1808 Every element consists of indivisible particles called atoms
James Clerk Maxwell (1831-1879)-1865 Maxwell’s field equations –
The birth of field theory (from Faraday)The electromagnetic theory of light-Light propagates as waves
Johann Balmer (1825-1898)-1885 Discovers numerological relationship between frequency
and prominent spectral lines of hydrogen:
Development of quantum theory
n = integerν = frequencyc = speed of lightR = Rydberg constant
Michael Faraday (1831), the electromagnetic field
William Thomson, the first Baron Kelvin
Wilhelm Conrad Roentgen (1845-1923)-1895 Demonstrates X-rays in experiments with passing electric current through low- pressure gas
First Nobel Prize in Physics!
J.J. Thompson (1856-1940)-1897 Identifies “cathode rays” as negative particles = electrons
“The more important fundamental laws and facts of physical science have all been discovered, and these are now so firmly established that the possibility of their ever being supplanted in consequence of new discoveries is exceedingly remote . . . Our future discoveries must be looked for in the sixth place of decimals.”
Albert A. Michelson, 1894
“There is nothing new to be discovered in physics now. All that remains is more and more precise measurement.”
William Thomson (Lord Kelvin), 1900
John William Strutt, 3rd Baron Rayleigh – Rayleigh scattering, Rayleigh waves, the theory of sound (his son was Robert John Strutt, 4th Baron Rayleigh – electrons and gases, radiation)
Lord Rayliegh (1842-1919) and James Jeans (1877-1946)-1900 Calculation of black body radiation
“Ultraviolet catastrophe”
Max Plank (1858-1947)-1901 Introduces the quantum concept -
Absorption and emission of radiant energy in discrete packets
“An indispensable hypothesis, even though still far from being a guarantee of success, is however the pursuit of a specific aim, whose lighted beacon, even by initial failures, is not betrayed. For many years, such an aim for me was to find the solution to the problem of the distribution of energy in the normal spectrum of radiating heat.”
– Nobel Lecture of Max Plank (1920)
E = hνh = 6.6262 x 10-34 kg m2 / sec
Albert Einstein (1879-1955)-1905 Photoelectric effect and the
photon concept…Special relativity too!
Ernest Rutherford (1871-1937)-1911 An atom consists of a
positively charged nucleus and negatively charged electrons orbiting the nucleus at constant speed
Niels Bohr (1885-1962)-1913 Quantum model of hydrogen
(early quantum theory)
Predicts the Rydberg constant and the line spectra for gaseous hydrogen
Bohr’s Three Postulates:
1) There are certain orbits in which the electron is stable and does not radiateThe energy of an electron in an orbit can be
calculated - that energy is directly proportional to the distance from the nucleus
Bohr simply forbids electrons from occupying just any orbit around the nucleus such that they can’t lose energy and spiral in…
2) When an electron falls from an outer orbit to an inner orbit, it loses energy…expressed as a quantum of electromagnetic radiation
3) A relationship exists between the mass, velocity and distance from the nucleus of an electron and Planck’s quantum constant…
From these principles, Bohr realized he could calculate the energy corresponding to an orbit:
m = mass of electrone = charge of electronħ = h / 2π
If an electron jumps from orbit n=2 to orbit n, the energy loss is:
energy is radiated, and expressing Plank’s relationship in terms of angular frequency (ω), rather than frequency (ν):
Bohr theoretically has expressed Balmer’s formula and could calculate the Rydberg constant knowing m, e, c, and ħ
Modern quantum theory:
Louis de Broglie (1892-1987)-1924 wave theory of matter
ultimately led to the development of wave mechanics
Wolfgang Pauli (1900-1958)-1925 the exclusion principle
No two electrons can be in the same place at the same time
Electrons in an atom can be described by four quantum numbers
No two electrons in an atom can have the same set of quantum numbers
λ particle wavelength
h Planck’s constant
p particle momentum
m rest mass
ν particle velocity
Predicted the neutrino!
Werner Heisenberg (1901-1976)-1925 matrix mechanics
Observables are the sole source of change-State vector does not change with time
Erwin Schrödinger (1887-1961)-1926 wave mechanics
states are the sole source of change
Max Born (1882-1970)-1926 Waves are probability waves
Paul Dirac (1902-1984)-1925-28Quantum field theory
Resolved particle-wave duality
Predicted antimatter
The relativistic quantum mechanical wave function (a relativistic generalization of the Schrodinger equation):
Bethe equation:
Hans Bethe (1906-2005)-1930 Evaluates passage of charged particles through matter
From first Born approximation:Bethe’s ionization equation – the probability of ionization of a given shell (nl)
Describes energy loss of charged particle with distance …
Development of concepts - SEM
Ernst Abbe (1840-1905)-1878 Geometric optics and the
resolving power of a microscope
What is resolution?
All lens images are diffraction patterns (circular slit diffraction)
An image point will be a disk, surrounded by diffraction rings representing diffraction maxima and minima
Rayleigh Criterion: Central maximum produced by one object point must exceed the first diffraction minimum of the other object point…
fully resolved just resolved unresolved
Airy Disk
O’
O
I’
Ii
A
B
θ
O’
O
si
To A
To B
d
Extreme rays from O’ to I differ by 1.22λ, so …
Total path difference is then…
At small angles…
The Abbe equation
and
Here, n is the refractive index
1) Visible light λ = 560 nm, for aperture angle of 0.9, and n = 1…
2) Electrons (remember de Broglie and the wave theory of matter) λ = 0.0054 nm…
True resolution depends on
1) Beam brightness
2) Lens aberrations
3) Scattering in specimen
Electron voltage (kV)
Relativistic Mass (EU)
Wavelength (nm)
Abbe resolution (Å)
5 1.0097 1.726e-2 10.563
10 1.0195 1.214e-2 7.433
20 1.0391 8.507e-3 5.206
50 1.0978 5.235e-3 3.204
200 1.3913 2.325e-3 1.423
400 1.7827 1.452e-3 0.889
Mass of an electron = 9.1091 X 10-31 kgSpeed of light = 299,790,000 meters/secondEnergy of an electron = 1.602 X 10-19 Newton meters/secondPlanck's Constant = 6.6256 X 10-34
Accelerating voltage physics calculator, University of Oklahoma electron microscopy laboratory
Louis de Broglie and the wave theory of matter allow the introduction of the basic concept of electron microscopy, but before that…
-1913 Henry Moseley (1887-1915)Following Bohr’s work, he demonstrates that the wavelengths of emitted X-rays correlates with atomic number
-1914 Max von Laue (1879-1960) shows that a beam of X-rays passing through a crystal produces a diffraction pattern.
Moseley’s Law:
f= frequency, Z = atomic #
k1 and k2 are constants
-1915 William Bragg (1864-1942) and his son, W. Lawrence Bragg (1890-1971) pioneer the analysis of crystal structure using X-ray diffraction.
d
-1914 Karl Siegbahn (1886-1978) Discovered M-series of wavelengths in X-ray emission spectra, and developed methodology and instrumentation for detailed X-ray spectroscopy.
SEM and EPMA development
1926 – Hans Busch establishes geometrical electron optics theoretically
1927 – Hugo Stintzing develops the cathode-ray scanning microphotometer, and essentially develops the concept of the scanning electron microscope
1928 – Ernst Ruska experimentally demonstrates electromagnetic focusing.
1931 – Max Knoll and Ernst Ruska build the first transmission electron microscope (Berlin) (receives Nobel Prize…1986)
“conventional” TEM, not scanning
1938 - Manfred von Ardenne
Credited with developing the first scanning electron microscope
The first commercial electron microscope is introduced by Siemens
1942 – Vladimir Zworykin, James Hillier, and R.L.Snyder develop the first thick specimen SEM at RCA labs
1931 – Johann and Cauchois develop sem-focusing spectrometers by bending multilayer structures.
1932 – Johansson develops the focusing spectrometer by bending a crystal to twice the radius if the focusing circle, then grinding to achieve full focus.
Vladimir Zworykin TV!
1943 – James Hillier develops the concept for electron probe microanalysis – the use of a focused electrons impinging on a specimen and their utility in chemical characterization.
1949-1951 Raimond Castaing develops the concept for electron-probe, X-ray microanalysis (using characteristic X-rays for chemical analysis), and builds the first electron microprobe in Paris
This becomes the basis for the first commercial instrument, introduced by Cameca in 1956
1965 – First commercial SEM is offered by Cambridge Instruments
(The first commercial TEM had been introduced by Philips Electron Optics in 1949)
Many commercial SEMs today:JEOL (Japan Electron Optics Lab)HitachiCarl Zeiss
Cambridge Instruments + Wild Leitz = Leica (1990)Carl Zeiss + Leica = LEO (1995)LEO integrated into Carl Zeiss (2004)Carl Zeiss acquires ALIS (2006)
FEI FEI and Philips Electron Optics merge 1997FEI acquires Micrion 1999
TescanCamscanTopcon / ISI
ALIS
1960s brought expansion of electron microprobe technology and commercial availability:
Cameca
JEOL
Cambridge Instruments
Advanced Metals Research
Applied Research Laboratories
Elion Instruments
Materials Analysis Company
Hitachi
Only Cameca and JEOL offer dedicated electron microprobes today
SEM technology today:
Ultra-high resolution (now to 0.4-0.5nm, Hitachi S-5500)
Cold field emission Schottky emission
Variable pressure
SEM technology today:
Extreme high resolutionSub nm image resolution for full voltage rangeAnalytical current capability(FEI Magellan)Energy filtered Schottky emission
STEM / SEM
Sidewall spacer
Poly Si
Ti barrier
Al lineW contact
Electron BackScatter Diffraction (EBSD)
Quartz orientation map
Combined FIB / SEM (dual beam)
The synergistic approach:EPMA+FIB+APT
Helium ion microscope – ultra high resolution microscopyAchieved 0.24nm image resolution
