Question: How many steps is the photoelectric effect in crystalline material broken into?
About the article "Photoelectric effect", section "Three-step model".

Candidate passages:
In the X-ray regime, the photoelectric effect in crystalline material is often decomposed into three steps:
 Inner photoelectric effect (see photodiode below).
The hole left behind can give rise to auger effect, which is visible even when the electron does not leave the material.
In molecular solids phonons are excited in this step and may be visible as lines in the final electron energy.
The inner photoeffect has to be dipole allowed.
The transition rules for atoms translate via the tight-binding model onto the crystal.
They are similar in geometry to plasma oscillations in that they have to be transversal.
 Ballistic transport of half of the electrons to the surface.
Some electrons are scattered.
 Electrons escape from the material at the surface.
In the three-step model, an electron can take multiple paths through these three steps.
All paths can interfere in the sense of the path integral formulation.
For surface states and molecules the three-step model does still make some sense as even most atoms have multiple electrons which can scatter the one electron leaving.
Video camera tubes in the early days of television used the photoelectric effect, for example, Philo Farnsworth's "Image dissector" used a screen charged by the photoelectric effect to transform an optical image into a scanned electronic signal. 
The piezooptic effect is manifest as a change in refractive index, n, of a material caused by a change in pressure on that material.
Early demonstrations of the piezooptic effect were done on liquids.
The effect has since been demonstrated in solid, crystalline materials. 
The photoelectric effect is the observation that many metals emit electrons when light shines upon them.
Electrons emitted in this manner may be called "photoelectrons".
According to classical electromagnetic theory, this effect can be attributed to the transfer of energy from the light to an electron in the metal.
From this perspective, an alteration in either the amplitude or wavelength of light would induce changes in the rate of emission of electrons from the metal.
Furthermore, according to this theory, a sufficiently dim light would be expected to show a lag time between the initial shining of its light and the subsequent emission of an electron.
However, the experimental results did not correlate with either of the two predictions made by this theory.
Instead, as it turns out, electrons are only dislodged by the photoelectric effect if light reaches or exceeds a threshold frequency, below which no electrons can be emitted from the metal regardless of the amplitude and temporal length of exposure of light.
To make sense of the fact that light can eject electrons even if its intensity is low, Albert Einstein proposed that a beam of light is not a wave propagating through space, but rather a collection of discrete wave packets (photons), each with energy "hf".
This shed light on Max Planck's previous discovery of the Planck relation () linking energy ("E") and frequency ("f") as arising from quantization of energy.
The factor "h" is known as the Planck constant.
In 1887, Heinrich Hertz discovered that electrodes illuminated with ultraviolet light create electric sparks more easily.
In 1905 Albert Einstein published a paper that explained experimental data from the photoelectric effect as being the result of light energy being carried in discrete quantized packets.
This discovery led to the quantum revolution.
Einstein was awarded the Nobel Prize in 1921 for "his discovery of the law of the photoelectric effect".
The photoelectric effect requires photons with energies from a few electronvolts to over 1 MeV in elements with a high atomic number.
Study of the photoelectric effect led to important steps in understanding the quantum nature of light and electrons and influenced the formation of the concept of wave–particle duality.
Other phenomena where light affects the movement of electric charges include the photoconductive effect (also known as photoconductivity or photoresistivity), the photovoltaic effect, and the photoelectrochemical effect. 
Polyglycolide is characterized by hydrolytic instability owing to the presence of the ester linkage in its backbone.
The degradation process is erosive and appears to take place in two steps during which the polymer is converted back to its monomer glycolic acid: first water diffuses into the amorphous (non-crystalline) regions of the polymer matrix, cleaving the ester bonds; the second step starts after the amorphous regions have been eroded, leaving the crystalline portion of the polymer susceptible to hydrolytic attack.
Upon collapse of the crystalline regions the polymer chain dissolves.
When exposed to physiological conditions, polyglycolide is degraded by random hydrolysis, and apparently it is also broken down by certain enzymes, especially those with esterase activity.
The degradation product, glycolic acid, is nontoxic, and it can enter the tricarboxylic acid cycle, after which it is excreted as water and carbon dioxide.
A part of the glycolic acid is also excreted by urine.
Studies undergone using polyglycolide-made sutures have shown that the material loses half of its strength after two weeks and 100% after four weeks.
The polymer is completely resorbed by the organism in a time frame of four to six months.
Degradation is faster in vivo than in vitro, this phenomenon thought to be due to cellular enzymatic activity.