Question: The crystalline material's photoelectric effect consists of how many steps?
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. 
Background radiation doses in the immediate vicinities of particles of high atomic number materials, within the human body, have a small enhancement due to the photoelectric effect. 
In a 1905 paper, Einstein postulated that light itself consists of localized particles ("quanta").
Einstein's light quanta were nearly universally rejected by all physicists, including Max Planck and Niels Bohr.
This idea only became universally accepted in 1919, with Robert Millikan's detailed experiments on the photoelectric effect, and with the measurement of Compton scattering.
Einstein concluded that each wave of frequency "f" is associated with a collection of photons with energy "hf" each, where "h" is Planck's constant.
He does not say much more, because he is not sure how the particles are related to the wave.
But he does suggest that this idea would explain certain experimental results, notably the photoelectric effect. 
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.