PHYSICS 412

SOLID STATE PHYSICS

Instructor: Dr. Ronald F. Brown

Office: Sci. Bldg. 52-D47 email: rbrown@calpoly.edu

Dept. Office 756-2065 http://www.calpoly.edu/~rbrown

Office Hours: MW 3-4; TuTh 11-12

Text: Brown, SOLID STATE PHYSICS - An Introduction for Scientists and Engineers

El Corral - Revised Fall, 2006

References: Listed on last page of the introduction section of the textbook.

Newton’s laws tell us how matter behaves when it is acted on by forces. The only two things we need to know about the physical world that Newton’s laws don’t tell us are: What is the nature of matter? What is the nature of forces that act between bits of matter? These two questions are still the central concerns of physics.

- David Goodstein, Caltech

THE QUANTUM THEORY AND ATOMIC PHYSICS

The essential ideas of solid state physics can be traced to the behavior of the electrons within atoms and to the ways in which electrons are shared between atoms and how they interact with the atoms in a solid and with each other. To describe their behavior requires the use of the quantum theory. Understanding the electronic structure of atoms leads to the periodic table and the various bonding mechanisms. And all the properties of solids ultimately depend on the bonding mechanisms between the atoms and how the electrons interact with those atoms and with each other.

STRUCTURAL PROPERTIES OF SOLIDS

The various structures associated with crystalline solids are ultimately related to the bonding mechanisms between the atoms. An understanding of why nature selects certain preferred crystal structures will lead to explanations of both the mechanical and electrical properties of the related solids. X-ray diffraction will be explored as the tool used to determine crystal structures.

MECHANICAL AND THERMAL PROPERTIES OF SOLIDS

The bonding mechanisms and crystal structures lead to important conclusions about such mechanical properties of solids as compressibilities, thermal expansion coefficients, mechanical wave propagation speeds, thermal conductivity and molar heat capacities. And the temperature dependence of the molar heat capacity will become an important tool for determining how the atoms vibrate. And it is the vibrational behavior of the atomic lattice that ultimately yields the temperature dependence of the electrical conductivity of metals - and plays a role in the mechanism associated with superconductivity.

ELECTRONIC PROPERTIES OF SOLIDS

The study of electrons in metals will lead to discussions of electrical and thermal conductivity, Hall effect, electron heat capacity, and superconductivity. The band theory of solids and the distinction between metals, insulators and semiconductors will follow from the discussion of the behavior of electrons in crystalline solids. The discussion of semiconductors will include band descriptions, intrinsic carrier concentration and the Fermi level, the effects of doping, electron and hole conductivity, Hall effect, optical absorption, and the physics of the pn junction. The course will conclude with a discussion of the equilibrium pn junction diode and the effects of bias voltages, temperature changes, and light absorption - an application of the ideas of band theory to the operation of basic junction devices.

COURSE FORMAT

CLASS MEETINGS - Each meeting will include some lecture and some discussion. It is expected that you will have read the appropriate material and worked on the related problems. The discussions can then deal with any material that is difficult to understand and with explanations and justifications for the developed lines of reasoning. How profitable the class meetings are depend very much on your level of preparation and on your participation. The class will benefit from the questions that you raise for discussion.

HOMEWORK - Learning is not a passive experience. Homework problems are most effective when they are being worked on while the material is being discussed. You are welcome to work together on homework assignments - but you should understand and be able to explain the work you do. The course is not primarily a problem solving course or a “skills” course - but rather deals with the ideas of solid state physics. But those ideas can often be explained in the context of problems. You will need to be able to explain and justify the work you do on problems. You will benefit from deciding, in each case, why that particular problem was assigned. It is never just to take up your time doing some task.

Maintain a problem notebook - a place where you work problems and keep your homework solutions together. You should complete at least 75% of the assigned homework while the related material is being discussed. Although some problems will be submitted and marked for feedback, homework will count only marginally toward your grade. But I may want to look at your notebook sometime. Expect that some problems will be submitted for grader feedback.

QUIZZES - There will be occasional take-home self-check quizzes. They will not be collected and will not count toward your grade but will help you learn the material. They should be taken as if they were closed book work alone exams. Write out explanations and justifications - make the connections - that is what you will need to be able to do on the exams. If you are unsure of yourself on these questions and problems, you are not yet prepared on that material – and should ask about them.

EXAMS - There will be two mid-term exams in addition to a final exam. Exams will be conceptual as well as involve some problem solving - and will require that you clearly and carefully justify your work. Grades on the exams will depend on the quality of your explanations. One of the tests may be take-home to allow more time on the exam and to make better use of class time. Let me know if you see a problem with take-home exams.

FINAL EXAM - Monday, December 8 4 – 7 pm

The final exam will be a three hour in-class exam and will be comprehensive, although weighted toward the electronic properties of solids. It will be “count” approximately as 1 1/2 hour exams - but that is less important than that it is the last opportunity to show that the ideas of the course have come together.

If you know that you will be unable to take an exam (or submit a take-home, if we have them), you will need to make prior arrangements. If an sudden illness or some other last minute emergency prevents you from taking a scheduled exam, leave a message at my office on the day of the exam or contact me by email as soon as possible.

PHYSICS 452 LABORATORY - Winter Quarter

The Physics 452 laboratory is designed to follow this course in sequence and will be taught Winter quarter. Much of the lecture course material is required to adequately analyse experiments. It is a good lab with small enrollment and lots of interaction among students and with the instructor. It is a good review of the essential material, and strongly reinforces the ideas of the lecture course. For scheduling purposes, please let me know if you intend to take the laboratory in the Winter quarter.

PHYSICS 413 - ADVANCED TOPICS IN SOLID STATE PHYSICS - Winter 2008

This course covers the last three chapters of the book - solid state devices, magnetic properties of solids, and superconductivity will be offerred . These topics are an exciting extension of the material covered in the first course of solid state physics. In addition, several of the experiments in the solid state laboratory relate to topics appearing in Physics 413.

For more information about this course, see: http://www.calpoly.edu/~rbrown/phys413.html

COURSE OBJECTIVES

An active participation in this course in solid state physics should yield an understanding of:

1. The interplay between theory and experiment in building an understanding of the nature of solids and their properties.

2. The essential features of the quantum theory which lead to our understanding of the behavior of electrons in solids.

3. The relationship between interatomic interaction mechanisms and the crystal structures of solids.

4. The essential elements of analysis of crystal structures using x-ray diffraction techniques.

5. The relationship between atomic bonding and various mechanical, thermal, and electronic properties - including both vibrational and electron heat capacities, electrical resistivities, etc.

6. The basic electrical properties of solids based on the quantum theory - including the development of the density of states and Fermi functions, conductivity, electronic heat capacity, and ultimately the band theory of solids and its interpretations.

7. The distinctions between metals, insulators, and semiconductors and the fundamental reasons for those distinctions based both on bonding mechanisms and the band theory of solids.

8. The properties of semiconducting materials - including the concentration of carriers, n- and p- type semiconductors, hole conductivity, optical absorption, and temperature effects - which allow the development of solid state devices.

9. The equilibrium pn junction in semiconductor diodes - and the effect on the equilibrium diode of applying bias voltages, raising the temperature, and bathing it in light. The basic operation of pn junction devices and of both bipolar and field effect transistors as amplifiers.

GRADES

The grade you receive in the course should reflect your overall performance in the course and your level of understanding of the course material. If this class is typical, most grades assigned will be in the A-C range. The grade I (incomplete) will be assigned only if there is an acceptable reason for a specific deficiency which can then be made up in a reasonable amount of time. Except in extraordinary circumstances, an incomplete must be made up within the following quarter.

Finally, it is important that you approach the study of solid state physics systematically. The study requires assimilating information from many different sources. Information that occurs early in the study (quantum theory, atomic bonding and crystal structure, mechanical and thermal properties) continues to be important throughout the discussions of the electronic properties of both metals and semiconductors.

Learning solid state physics is not a spectator sport. It is important that you make good use of the questions and problems at the end of each chapter. The point is not to complete assignments, but learn from them. Every problem that is assigned is assigned for a reason. Look at each assigned problem and try to determine WHY it was assigned. What, exactly, was to be learned from doing that problem? This is not a skills course, where you are asked to learn techniques for solving specific problems, but rather a thinking course. The reading, lectures, and problems are intended to help you develop an understanding of the properties of solids and how those properties allow the development of important and fascinating devices and to make you conversant with the principles and ideas.

PHYSICS 412 ASSIGNMENTS

Fall 2008

Chapter 1: Sects. 2-4; Problems 4, 5, 7, 8, 11, 13, 14

Chapter 2: Sects. 1-3,5; Problems 1, 2, 4, 5, 7, 8, 9, 11

Chapter 3: Sects. 1-4; Problems 1, 2, 5, 6, 8

Chapter 4: Sects. 1,3,4; Problems 1, 2, 6, 7, 8, 9, 15, 16

EXAM 1 Chapters 1-4

Chapter 5: Sects. 1,3-5 Problems 1, 3, 5, 7, 9, 10, 11, 13, 14, 15, 18, 20

Chapter 6: Sects. 1-3,5 Problems 1, 2, 4, 7, 8

EXAM 2 Chapters 5,6

Chapter 7: Sects. 1-5 Problems 1, 2, 3, 4, 6, 7, 9, 12

REVIEW QUESTIONS: There are a number of conceptual review questions at the end of the book - following chapter 10 - that might help you review for the final exam.

FINAL EXAM: Monday, December 8 4 – 7 pm

The final exam is comprehensive with emphasis on the electrical and electronic properties of solids. The final will count about 1 1/2 midterm exams. You must pass the final exam to pass the course.

HOMEWORK POLICY: Homework will count only marginally toward your grade. It is assigned to help you learn the material. You are welcome to work together on homework - but you should understand and be able to explain the work you do. In doing problems, write out explanations carefully, making the connections between the ideas. It is only then that you will know you understand it. Maintain a problem notebook so that you have a complete set of worked problems to refer to as well as an accurate record of your effort in the course - and to show me if you have difficulties in the course. I may ask to see your problem book at the end of the quarter. Every problem has been assigned for a reason. It is expected that you will complete at least 75% of the assigned problems while the related material is being discussed.

GRADES: The grade you are assigned will reflect your overall performance in the class as measured by the exams and final and on your level of understanding of the course material and attainment of the course objectives.