Passivation (chemistry)

passivationsurface passivationpassivatingpassivation layerpassivatedpassivatepassivepassivatespassivantpassive layer
Passivation, in physical chemistry and engineering, refers to a material becoming "passive," that is, less affected or corroded by the environment of future use.wikipedia
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Corrosion

corrosion resistancecorrodecorrosive
As a technique, passivation is the use of a light coat of a protective material, such as metal oxide, to create a shell against corrosion.
As a result, methods to reduce the activity of the exposed surface, such as passivation and chromate conversion, can increase a material's corrosion resistance.

Aluminium

aluminumAlall-metal
Corrosion coating reduces the rate of corrosion by varying degrees, depending on the kind of base metal and its environment, and is notably slower in room-temperature air for aluminium, chromium, zinc, titanium, and silicon (a metalloid); the shell of corrosion inhibits deeper corrosion, and operates as one form of passivation. Pure aluminium naturally forms a thin surface layer of aluminium oxide on contact with oxygen in the atmosphere through a process called oxidation, which creates a physical barrier to corrosion or further oxidation in many environments.
Aluminium is remarkable for its low density and its ability to resist corrosion through the phenomenon of passivation.

Oxide

oxidesmetal oxideO
The inert surface layer, termed the "native oxide layer", is usually an oxide or a nitride, with a thickness of a monolayer of 0.1-0.3 nm (1-3 Å) for a noble metal such as platinum, about 1.5 nm (15 Å) for silicon, and nearer to 5 nm (50 Å) for aluminium after several years.
For example, aluminium foil develops a thin skin of Al 2 O 3 (called a passivation layer) that protects the foil from further corrosion.

Semiconductor device fabrication

fabricatedsemiconductor fabricationsemiconductor manufacturing
Surface passivation refers to a common semiconductor device fabrication process critical to modern electronics. He developed the surface passivation process, a new method of semiconductor device fabrication that involves coating a silicon wafer with an insulating layer of silicon oxide so that electricity could reliably penetrate to the conducting silicon below.
It is a multiple-step sequence of photolithographic and chemical processing steps (such as surface passivation, thermal oxidation, planar diffusion and junction isolation) during which electronic circuits are gradually created on a wafer made of pure semiconducting material.

Mohamed M. Atalla

Mohamed AtallaMartin Mohamed AtallaMohamed Mohamed Atalla
Also known as the Atalla passivation technique, the surface passivation process was originally developed by Mohamed M. Atalla at Bell Labs in the late 1950s.
Most importantly, his invention of the MOSFET (metal–oxide–semiconductor field-effect transistor, or MOS transistor) in 1959, along with his earlier surface passivation and thermal oxidation processes (the basis for silicon semiconductor technology such as the monolithic integrated circuit chip), revolutionized the electronics industry.

Silicon

Sisilicon revolutionsilicium
Passivation can occur only in certain conditions, and is used in microelectronics to enhance silicon.
A breakthrough in silicon semiconductor technology came with the work of Egyptian engineer Mohamed M. Atalla, who developed the process of surface passivation by thermal oxidation at Bell Labs in the late 1950s.

Titanium

Tititanium oretitanian
Corrosion coating reduces the rate of corrosion by varying degrees, depending on the kind of base metal and its environment, and is notably slower in room-temperature air for aluminium, chromium, zinc, titanium, and silicon (a metalloid); the shell of corrosion inhibits deeper corrosion, and operates as one form of passivation.
It is, however, slow to react with water and air at ambient temperatures because it forms a passive oxide coating that protects the bulk metal from further oxidation.

Chromium

Crchromechromium(III)
Corrosion coating reduces the rate of corrosion by varying degrees, depending on the kind of base metal and its environment, and is notably slower in room-temperature air for aluminium, chromium, zinc, titanium, and silicon (a metalloid); the shell of corrosion inhibits deeper corrosion, and operates as one form of passivation.
Chromium metal left standing in air is passivated, i.e. forms a thin, protective, surface layer of oxide.

Zinc

ZnZn 2+ zinc alloy
Corrosion coating reduces the rate of corrosion by varying degrees, depending on the kind of base metal and its environment, and is notably slower in room-temperature air for aluminium, chromium, zinc, titanium, and silicon (a metalloid); the shell of corrosion inhibits deeper corrosion, and operates as one form of passivation.
The surface of the pure metal tarnishes quickly, eventually forming a protective passivating layer of the basic zinc carbonate, by reaction with atmospheric carbon dioxide.

Thermal oxidation

controlled oxidationthermal oxide thermally grown oxide
This is typically achieved using a form of thermal oxidation.
The thermal oxidation process was developed in the late 1950s by Egyptian engineer Mohamed Atalla, who initially used it for the surface passivation of silicon semiconductors, before he later used the process to fabricate the first MOSFETs (metal-oxide-semiconductor field-effect transistors) with Dawon Kahng at Bell Labs.

MOSFET

metal-oxide-semiconductorMOSMOS integrated circuit
It is commonly used to manufacture MOSFETs (metal-oxide-semiconductor field-effect transistors) and silicon integrated circuit chips (with the planar process), and is critical to the semiconductor industry.
This is known as surface passivation, a method that later became critical to the semiconductor industry as it made possible the mass-production of silicon semiconductor technology, such as integrated circuit (IC) chips.

Corrosion inhibitor

corrosion inhibitorsrust inhibitorinhibitor
Some corrosion inhibitors help the formation of a passivation layer on the surface of the metals to which they are applied.
A common mechanism for inhibiting corrosion involves formation of a coating, often a passivation layer, which prevents access of the corrosive substance to the metal.

Planar process

planar technologyplanarmicrofabricated
It is commonly used to manufacture MOSFETs (metal-oxide-semiconductor field-effect transistors) and silicon integrated circuit chips (with the planar process), and is critical to the semiconductor industry.
The process utilizes the surface passivation and thermal oxidation methods.

Carbon quantum dots

carbon quantum dot
Surface passivation is also critical to solar cell and carbon quantum dot technologies.
Carbon quantum dots (CQDs, C-dots or CDs) are small carbon nanoparticles (less than 10 nm in size) with some form of surface passivation.

Iron

FeFe 2+ Fe(III)
In the mid 1800s, Christian Friedrich Schönbein discovered that when a piece of iron is placed in dilute nitric acid, it will dissolve and produce hydrogen, but if the iron is placed in concentrated nitric acid and then returned to the dilute nitric acid, little or no reaction will take place.
Unlike the oxides of some other metals, that form passivating layers, rust occupies more volume than the metal and thus flakes off, exposing fresh surfaces for corrosion.

Solar cell

solar cellsphotovoltaic cellphotovoltaic cells
Surface passivation is also critical to solar cell and carbon quantum dot technologies.

Invention of the integrated circuit

development of integrated circuit chipsIC componentsIndependent invention
Before the development of integrated circuit chips, discrete diodes and transistors exhibited relatively high reverse-bias junction leakages and low breakdown voltage, caused by the large density of traps at the surface of single crystal silicon.
In turn, the basis for Hoerni's planar process were the surface passivation and thermal oxidation methods developed by Mohamed Atalla at Bell Labs during the late 1950s.

Wafer (electronics)

wafersilicon waferwafers
He developed the surface passivation process, a new method of semiconductor device fabrication that involves coating a silicon wafer with an insulating layer of silicon oxide so that electricity could reliably penetrate to the conducting silicon below.
This is known as surface passivation, a method that later became critical to the semiconductor industry as it made possible the mass-production of silicon integrated circuits (ICs).

Nitric acid

nitricHNO 3 aqua fortis
In the mid 1800s, Christian Friedrich Schönbein discovered that when a piece of iron is placed in dilute nitric acid, it will dissolve and produce hydrogen, but if the iron is placed in concentrated nitric acid and then returned to the dilute nitric acid, little or no reaction will take place.
The formation of this protective layer is called passivation.

Integrated circuit

integrated circuitsmicrochipchip
It is commonly used to manufacture MOSFETs (metal-oxide-semiconductor field-effect transistors) and silicon integrated circuit chips (with the planar process), and is critical to the semiconductor industry.
The monolithic integrated circuit chip was enabled by the surface passivation process, which electrically stabilized silicon surfaces via thermal oxidation, making it possible to fabricate monolithic integrated circuit chips using silicon.

Pourbaix diagram

(Pourbaix)Eh-pH diagramspotential-pH
The conditions necessary (but not sufficient) for passivation are recorded in Pourbaix diagrams.
Passivation occurs when the metal forms a stable coating of an oxide or other salt on its surface, the best example being the relative stability of aluminium because of the alumina layer formed on its surface when exposed to air.

Transistor

transistorstransistorizedsilicon transistor
Before the development of integrated circuit chips, discrete diodes and transistors exhibited relatively high reverse-bias junction leakages and low breakdown voltage, caused by the large density of traps at the surface of single crystal silicon.
This is known as surface passivation, a method that became critical to the semiconductor industry as it later made possible the mass-production of silicon integrated circuits.

Anodizing

anodizedanodized aluminumanodised
Generally, there are two main ways to passivate aluminium alloys (not counting plating, painting, and other barrier coatings): chromate conversion coating and anodizing.
Anodising (also spelled anodizing in American English) is an electrolytic passivation process used to increase the thickness of the natural oxide layer on the surface of metal parts.

Chromate conversion coating

zinc yellowchromate conversionchromating
Generally, there are two main ways to passivate aluminium alloys (not counting plating, painting, and other barrier coatings): chromate conversion coating and anodizing.
Chromate conversion coating is a type of conversion coating used to passivate steel, aluminium, zinc, cadmium, copper, silver, magnesium, and tin alloys.

Aluminium oxide

aluminaaluminum oxideAl 2 O 3
Pure aluminium naturally forms a thin surface layer of aluminium oxide on contact with oxygen in the atmosphere through a process called oxidation, which creates a physical barrier to corrosion or further oxidation in many environments.
Metallic aluminium is very reactive with atmospheric oxygen, and a thin passivation layer of aluminium oxide (4 nm thickness) forms on any exposed aluminium surface in a matter of hundreds of picoseconds.