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Welcome to ECE 360Introduction to the Solid State Physics and Devices

Lecturer: Goknur Cambaz Bukegoknurcambaz@gmail.comgoknur@cankaya.edu.tr

About me…

B.S.: Met. and Materials Engineering, METU

M.S.: Met. and Materials Engineering, METU

Ph.D.: Materials Science and Engineering -Nanotechnology Institute, Drexel University, Philadelphia, USA

Course Objectives

Basic principles of chemistry, physics and show how they apply in describing the behavior of the solid stateUnderstand the types of materials The relationship between electronic structure, chemical bonding, and crystal structureThe relationships between the structural elements of materials and their propertiesIntroducing many electrical, optical and magnetic phenomena and their applications in today’s technology

Course Material

William Callister, Materials Science and Engineering – An Introduction,John Wiley & Sons 2007………………………………………………………………

Donald A. Neamen, Semiconductor Physics and Devices,McGraw Hill 2003

Ben G. Streetman, Solid State Electronic Devices,Prentice Hall 20000-13-025538-6

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Grading

Homework: 0%Attendance: 10% (min 50% of att. required)Quiz: 20%Midterm: 20%Presentation: 20%Final Exam: 30%

CHAPTER 1 INTRODUCTION

Solid State Physics…

Si chiptransistors

Matter… Human Technological Prehistory:

The Stone Age

The Bronze Age Bronze is a metal alloy consisting primarily of copper, usually with tin as the main additive

The Iron Age Cutting tools and weapons were mainly made of iron or steel

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Nano Age… Engineering System

PERFORMANCE = f (design, construction)

choice of material

properties

composition+

atomic arrangement+

bonding

Carbon

Graphite Diamond Nanotubes

Space elevator

CHAPTER 2 ATOMIC STRUCTURE AND INTERATOMIC BONDING

Most of the properties of solid materials depend on:

geometrical atomic arrangementsinteractions among constituent atoms

or molecules

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~ 400 BC - Democritus

Ancient Greek philosopherDemocritus coined the term átomos which means "uncuttable" or "the smallest indivisible particle of matter".

Structure of MatterPhysical world

“VOID + BEING”

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1803 – John Dalton

English instructor and natural philosopher “Each element consists of atoms of single unique type and can join to form chemical compounds.”Originator of the modern atomic theory

1869 - MendeleevBuilding upon earlier discoveries by scientists, Mendeleev published the first functional PERIODIC TABLE. Certain chemical properties of elements repeat periodically when arranged by atomic number.

1869…

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Today: Periodic Table of the Elements The Structure of the Atom

Status report end of the 19th centuryAtom is electrically neutral Negative charge carried by electrons Electron has very small mass

bulk of the atom is positive, most mass resides in positive charge

The Structure of the Atommass (kg)charge (C)symbolparticle

9.11×10–31–1.6×10–19e–electron

1.675×10–270 noneutron

1.673×10–27+1.6×10–19p+proton

Question: what is the spatial distribution of charge inside an atom?

Models of Atom

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1897 – Sir J. J. Thomson

Discovered the electron (1906 Nobel Prize in Physics).

Plum Pudding (1904): “The atom as being made up of electrons swarming in a sea of positive charge.

Results:Majority of a particles transmitted (pass through) or deflected through small anglesTiny fraction deflected through large angles

1909 – E. RutherfordTested the Plum Pudding Model.

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Conclusion:Disproved the Plum-Pudding ModelLarge amount of the atom's charge and mass is concentrated into a small region Atom was mostly empty space

1909 – E. Rutherford

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Conclusion:Disproved the Plum-Pudding ModelLarge amount of the atom's charge and mass is concentrated into a small region Atom was mostly empty space

Objections to Rutherford modelThe laws of classical mechanics predict that the electron will release electromagnetic radiationwhile orbiting a nucleus. Because the electron would lose energy, it would gradually spiral inwards, collapsing into the nucleus. This atom model is unsuccessful, because it predicts that all atoms are unstable.

1909 – E. Rutherford

1912 – N. Bohr

Many phenomena involving electrons in solids could not be explained in terms of CLASSICAL MECHANICS.We need QUANTUM MECHANICS…

Quantum mechanics (QM) is a set of principles describing the physical reality at the atomic level of matter (molecules and atoms) and the subatomic (electrons, protons, and even smaller particles).

Bohr Postulates for the Hydrogen Atom

1. Rutherford atom is correct 2. Classical EM theory not applicable to orbiting e-3. Newtonian mechanics applicable to orbiting e-4. Eelectron = Ekinetic + Epotential

5. e- energy quantized through its angular momentum: L = mvr = nh/2π, n = 1, 2, 3,…

6. Planck-Einstein relation applies to e-transitions:∆E = Ef-Ei= hf = hc/λc = νλ

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Bohr Model of Atom

r(n) = const x n2/ZE(n) = -K x Z2/n2 K = 13.6 eVv(n) = const x Z/n

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Gas discharge tube containing hydrogen

A. Ångström

Gas discharge tube containing hydrogen

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An electron in Li2+ falls from n = 2 to the ground state.

(a) Calculate the wavelength of the emitted photon.

(b) Is it in the visible range of electromagnetic spectrum?

Matter – Energy Interaction

e- incident Kinetic en. of scattered electron

Photon energy = hc/λn=1 , ground state

n=2

n=3

n=∞ , represents free electron

Suppose E (incident) > ∆E(1→2)

e- scattered

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….break…

http://www.ptable.com/

Gas discharge tube containing hydrogen

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Hydrogen SpectrumAtomic spectra: When an electric discharge (spark) passes through a gas(H2), it excites the electrons of the atoms. The atoms then emit the absorbed energy in the form of light as the electrons return to a lower energy state. When a narrow beam of light is passed through a prism, a spectrum of colors as individual lines can be seen. This is called atomic spectrum or emission spectrum.

An electron in Li2+ falls from n = 2 to the ground state.

(a) Calculate the wavelength of the emitted photon.

(b) Is it in the visible range of electromagnetic spectrum?

1913 - Sommerfeld

German theoretical physicistModified the Bohr Model“suppose we have plurality of orbits” – a shell containing multiple orbits: ORBITALS How to capture these new ideas quantitatively?We need new quantum numbers: n, l, m, s

Shapes of Orbitals

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What is the filling sequence of electrons in orbitals by n, l, m, s is not adequate?

AUFBAU PRINCIPLE3 principles:

1. Pauli Exclusion Principle

2. Electrons fill orbitalsfrom lowest en. to highest en.

3. Hund’s rule

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Electron Energy States

1s

2s2p

K-shell n = 1

L-shell n = 2

3s3p M-shell n = 3

3d

4s

4p4d

Energy

N-shell n = 4

• have discrete energy states• tend to occupy lowest available energy state.

Electrons...

Adapted from Fig. 2.4, Callister & Rethwisch 8e.

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Electronic Configurationsex: Fe - atomic # = 26

valence electrons

Adapted from Fig. 2.4, Callister & Rethwisch 8e.

1s

2s2p

K-shell n = 1

L-shell n = 2

3s3p M-shell n = 3

3d

4s

4p4d

Energy

N-shell n = 4

1s2 2s2 2p6 3s2 3p6 3d6 4s2

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Electron ConfigurationsValence electrons – those in unfilled shellsFilled shells more stableValence electrons are most available for bonding and tend to control the chemical properties

example: C (atomic number = 6)

1s2 2s2 2p2

valence electrons

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• Why? Valence (outer) shell usually not filled completely.

• Most elements: Electron configuration not stable.

SURVEY OF ELEMENTS

Electron configuration

(stable)

...

... 1s 22s 22p 63s 23p 6 (stable)... 1s 22s 22p 63s 23p 63d 10 4s 24p 6 (stable)

Atomic #

18...36

Element1s 11Hydrogen1s 22Helium1s 22s 13Lithium1s 22s24Beryllium1s 22s 22p 15Boron1s 22s 22p 26Carbon

...1s 22s 22p 6 (stable)10Neon1s 22s 22p 63s 111Sodium1s 22s 22p 63s 212Magnesium1s 22s 22p 63s 23p 113Aluminum

...Argon...Krypton

Adapted from Table 2.2, Callister & Rethwisch 8e.

Wave mechanics to arrive at same place: E=E(n,l,m,s)

The Bohr model – significant limitationsResolution: Wave-mechanical model(electron is considered to exhibit both wave-like and particle-

like characteristics).De Broglie: “If a photon which has no mass, can behave as a particle, does an electron which has mass can behave as a wave (1920)?” λ = h/p = h/mvHeisenberg: Uncertainty Principle

“I don’t know where any of one of electrons is, but I can tell you an average where any of one of them is likely to be”Schrodinger

Bohr Postulates for the Hydrogen Atom

1. Rutherford atom is correct 2. Classical EM theory not applicable to orbiting e-3. Newtonian mechanics applicable to orbiting e-4. Eelectron = Ekinetic + Epotential

5. e- energy quantized through its angular momentum: L = mvr = nh/2π, n = 1, 2, 3,…

6. Planck-Einstein relation applies to e-transitions:∆E = Ef-Ei= hf = hc/λc = νλ

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Niels Bohr, Werner Heisenberg, and Wolfgang Pauli talking in the NielsBohr Institute lunchroom, possibly 1934 or 1936

Schrodinger Equation

Hydrogen 2s Radial Probability Comparison of Bohr and Wave mechanical atom models