write on structure of thin film?

Question

single crystal & bulk crystal and differant between them ?
disadvantages of preparation of thin film ?
impuirty
vacuum system

Answer 1

Single crystal is like the nearly flawless blue-white diamond I gave to my wife when I proposed marriage. Bulk crystal is like the fifty pound chunk of quartz she dug up in Arkansas a few yrars ago, some fairly large single crystals of quartz but with flaws and randomly oriented.

The semiconductor industry depends on the availability of large (12 inches diameter and larger) single-crystals of silicon, grown and pulled slowly in vacuum from a special furnace. These crystal boules are sliced into wafers and then semiconductor devices and electrical interconnections are either grown or deposited or implanted as thin films on the surface. Deliberate impurities are added in layers by a process called diffusion or by accelerated ion implant to create different electrical properties in the various layers.

Not all the processing is done in a high or ultra-high vacuum, but that is generally the starting point before a process is started.

Disadvantages of preparing thin films are difficulties with crystal lattice alignment, the time-cost to grow a thin film to the required thickness, and defects in the thin film that can render a large part of the wafer unusable.

As you cut and paste this answer for your paper, don't forget to include the buzz word epitaxial somewhere in there.