ECE 360 Introduction to the Solid State Physics and Devices

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Semiconductor Physics and Devices,. McGraw Hill 2003. ▫ Ben G. Streetman,. Solid State Electronic Devices,. Prentice Hall 20000-13-025538-6 ...

About me…

Welcome to ECE 360 Introduction to the Solid State Physics and Devices Lecturer: Goknur Cambaz Buke goknurcamba[email protected] [email protected]

Course Objectives „

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

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

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

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

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 „ „ „ „ „ „

CHAPTER 1 INTRODUCTION

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

Solid State Physics… transistors

Matter…

Si chip

Human Technological Prehistory: „

The Stone Age

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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 composition + atomic arrangement + bonding

properties

Carbon Space elevator

Graphite

Diamond

Nanotubes

CHAPTER 2 ATOMIC STRUCTURE AND INTERATOMIC BONDING Most of the properties of solid materials depend on: „ geometrical atomic arrangements „ interactions among constituent atoms or molecules

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~ 400 BC - Democritus „ „

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

Structure of Matter Physical world “VOID + BEING”

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1803 – John Dalton

1869 - Mendeleev „

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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

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Building 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 century „ Atom 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 Atom particle

symbol

charge (C)

mass (kg)

electron

e–

–1.6×10–19

9.11×10–31

proton

p+

+1.6×10–19

1.673×10–27

neutron

no

0

1.675×10–27

Models of Atom

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

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1897 – Sir J. J. Thomson

1909 – E. Rutherford „

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Discovered the electron (1906 Nobel Prize in Physics).

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

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Tested the Plum Pudding Model.

Results: ‰

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Majority of a particles transmitted (pass through) or deflected through small angles Tiny fraction deflected through large angles

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1909 – E. Rutherford „

Conclusion: ‰ ‰

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

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1909 – E. Rutherford „

Conclusion: ‰ ‰

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Objections to Rutherford model ‰

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1912 – N. Bohr „

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The laws of classical mechanics predict that the electron will release electromagnetic radiation while 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.

Bohr Postulates for the Hydrogen Atom

Many phenomena involving electrons in solids could not be explained in terms of CLASSICAL MECHANICS.

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We need QUANTUM MECHANICS…

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2. 3. 4.

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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).

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

Rutherford atom is correct Classical EM theory not applicable to orbiting eNewtonian mechanics applicable to orbiting eEelectron = Ekinetic + Epotential e- energy quantized through its angular momentum: L = mvr = nh/2π, n = 1, 2, 3,… Planck-Einstein relation applies to e-transitions: ∆E = Ef-Ei= hf = hc/λ c = νλ

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Bohr Model of Atom „ „ „

r(n) = const x n2/Z E(n) = -K x Z2/n2 K = 13.6 eV v(n) = const x Z/n

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A. Ångström

Gas discharge tube containing hydrogen

Gas discharge tube containing hydrogen

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Matter – Energy Interaction Suppose E (incident) > ∆E(1→2) „

(a)

(b)

An electron in Li2+ falls from n = 2 to the ground state. Calculate the wavelength of the emitted photon. Is it in the visible range of electromagnetic spectrum?

n=∞ , represents free electron

n=3

e- incident

Kinetic en. of scattered electron n=2

Photon energy = hc/λ

e- scattered

n=1 , ground state

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http://www.ptable.com/

….break…

Gas discharge tube containing hydrogen

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Hydrogen Spectrum Atomic 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.

1913 - Sommerfeld „ „ „

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(a)

(b)

An electron in Li2+ falls from n = 2 to the ground state. Calculate the wavelength of the emitted photon. Is it in the visible range of electromagnetic spectrum?

Shapes of Orbitals

German theoretical physicist Modified 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

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

3 principles: 1.

2.

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Pauli Exclusion Principle Electrons fill orbitals from lowest en. to highest en. Hund’s rule

Electron Energy States

Electronic Configurations

Electrons...

• have discrete energy states • tend to occupy lowest available energy state. 4d 4p

Energy

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

ex: Fe - atomic # = 4d 4p

N-shell n = 4

3d

3d

4s

4s

3p 3s 2p 2s 1s

M-shell n = 3

Energy

3p 3s

26 1s2 2s2 2p6 3s2 3p6 3d 6 4s2 N-shell n = 4 valence electrons

M-shell n = 3 Adapted from Fig. 2.4, Callister & Rethwisch 8e.

L-shell n = 2

2p 2s

L-shell n = 2

K-shell n = 1

1s

K-shell n = 1

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SURVEY OF ELEMENTS

Electron Configurations „ „ „

Valence electrons – those in unfilled shells Filled shells more stable Valence electrons are most available for bonding and tend to control the chemical properties ‰

• Most elements: Electron configuration not stable. Element Hydrogen Helium Lithium Beryllium Boron Carbon ...

example: C (atomic number = 6) 1s2

2s2

2p2 valence electrons

Atomic # 1 2 3 4 5 6

Electron configuration 1s 1 1s 2 (stable) 1s 2 2s 1 1s 2 2s 2 1s 2 2s 2 2p 1 1s 2 2s 2 2p 2 ...

Adapted from Table 2.2, Callister & Rethwisch 8e.

Neon Sodium Magnesium Aluminum ...

10 11 12 13

1s 2 2s 2 2p 6 (stable) 1s 2 2s 2 2p 6 3s 1 1s 2 2s 2 2p 6 3s 2 1s 2 2s 2 2p 6 3s 2 3p 1 ...

Argon ... Krypton

18 ... 36

(stable) 1s 2 2s 2 2p 6 3s 2 3p 6 ... 2 2 6 2 6 10 2 1s 2s 2p 3s 3p 3d 4s 4p 6 (stable)

• Why? Valence (outer) shell usually not filled completely. 61

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

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Bohr Postulates for the Hydrogen Atom

The Bohr model – significant limitations Resolution: Wave-mechanical model

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(electron is considered to exhibit both wave-like and particlelike characteristics).

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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/mv ‰ Heisenberg: 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 ‰

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4. 5.

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Rutherford atom is correct Classical EM theory not applicable to orbiting eNewtonian mechanics applicable to orbiting eEelectron = Ekinetic + Epotential e- energy quantized through its angular momentum: L = mvr = nh/2π, n = 1, 2, 3,… Planck-Einstein relation applies to e-transitions: ∆E = Ef-Ei= hf = hc/λ c = νλ

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Schrodinger Equation

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

Hydrogen 2s Radial Probability

Comparison of Bohr and Wave mechanical atom models

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