Application Of Zinc Oxide Nanostructures Biology Essay

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Spintronics is a combination of two things, spin magnetism and Electronics. The idea is behind use the spin of an electron. Basically electron has two spins, spin up or clockwise and spin down or anticlockwise. In future spin will help us to do more work as compare to electronics with great accuracy. Spin of an electron can be detected at weak magnetic energy.

Fig.1.1 Schematic overview of spintronics which combines both charge (electronics) and spin (magnetism) into a novel field of research and applications.

http://www.spintronics-info.com/introduction

spintronics play a vital role in solid sate physics, and possible devices that exploit spin properties along with charge degrees of freedom..

For example, spin relaxation and spin transport in metals and semiconductors are not only for basic solid state physics issues, but also for the already demonstrated potential these phenomena have in electronic technology.

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The device that is already in use in industry as a read head and a memory-storage cell is the Giant magneto-resistance (GMR)

GMR

It's consisting of alternating layers of ferromagnetic and non-magnetic sandwich.

The device resistance changes from low to high (from parallel to antiparallel magnetization) based on relative orientation of magnetization between magnetic layers. This change is known as magnetoresistance which is used to detect changes in magnetic field.

Latest GMR technology have also involved magnetic tunnel junction device and current of this magnetic tunneling junction depend upon how electrodes are oriented.

Two approaches are used to design spintronic devices.

This GMR based technology used either those new materials have larger spin polarization of electrons or by making some changes in already working devices so that better result can be achieved.

The second approach is more fundamental, searching new ways for generation and utilization of spin-polarized currents. It works for finding spin transport in semiconductors and searching new ways so that a semiconductor behaves like a spin polarizer or spin-valve. This approach is important because already working metal-based devices do not enhance the signals but semiconductor based spintronic devices do so, generally multi-function devices. Besides of all this semiconductor based devices could not be easily fabricated with typical semiconductor technology.

Advantages

There are some advantages to come semiconductor with spintronic based devices. For example the cause of hindrance for spin transport at a contacting point when a semiconductor in contact with another material is clear now. In earlier days, the plan of action to understand the further action of spin transport in hybrid semiconductor transport was taking from historic magnetic materials. However there is another approach to check out the spin transport in all semiconductor devices geometries. In that type of synopsis a composite of optical manipulation (bright circular polarized light which is used to produce total spin polarization) and material inhomogeneities (for example introduction of impurities in a afresh ternary ferromagnetic compound Ga1-xMnxAs in which Mn is impurity) can be used to modify the spin transport properties.

http://www.physics.umd.edu/rgroups/spin/intro.htm

Uses

There are number of uses of spintronics. One of them is most commonly used is storage. MRAM worked upon spintronics theory, and it affirms to be fast, portable and non-volatile memory. Scientists working upon to make spintronics based transistors for the circuits instead of electronic based circuits.

Now a days Hard-Disks and sensors have Spin-Valves which is spintronics.Everspin selling 4-Mbiits modules.

http://www.spintronics-info.com/introduction

Diluted Magnetic Semiconductor (DMS)

Traditional semiconductors doped with transition metals

Why "Dilute"?

Small doping concentration (a few %)

Why "Magnetic"?

Display ferromagnetisation

Why "Semiconductor"?

While preserving the semiconducting properties

Dilute mean very small amount of impurities from the transition metals up to≤10%

The selections of materials for the semiconductor spintronics two things are important.

At room temperature FM behavior should remain same.

It would be worth of cost if there were already existing technology base for the materials in other applications.

(D. J. Craik, Magnetic Oxides (Wiley New York, 1975).

However, structures of those composites are di_erent from Si or GaAs, the crystals are very hard to produce in experiment, their low Curie temperature Tc (50K or lower), strong insulation and poor semi conducting trans-port property further hampered their value in application.

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(H. Ohno, Science 281, 951 (1998)).

Now a days diluted magnetic semiconductors are composite of transition metal (mainly Mn) doped II-VI, IV-VI and II-V compound semiconductors, typical examples are: II-VI: (Zn,Mn)Se, (Cd,Co)Se, (Hg,Fe)Te; IV-VI: (Sn,Mn)Te, (Pb,Mn)Te, (Pb,Eu)Te, etc. Mn doped II-VI semiconductors are especially focused on, typical materials are (Zn,Mn)Se etc.

Possible Dilute Materials (Transition Metal)

Manganese

Chromium

Vanadium

Iron

Cobalt

Nickel

History of Zinc

Zinc was invented by Olof Bergman of Uppsala, in the 18th century, because metallic zinc lacked a traditional symbol.

A Swiss alchemist Theophrastus Bombastus von Hohenheim (Paracelsus, 1493-1541), named it Zinc, who mold the new Latin word zincum from ancestors that is not clear yet. As it was necessary to give some name of this discovered metal to distinguish it, although along time ago its alloy, brass were well known. Different languages have different name and pronunciations for the Zinc,

In English and Spanish it is "zinc"

In German and Dutch "Zink"

In Spanish "cinc"

In Welsh "sinc" (pronounced as "shink"

In Greek pseudargyros ("false silver") or tsigkos, pronounced "tsingos"

In Russian "tsink"

The kitchen sink has nothing to do with zinc, unless it happens to be made from it.

It is forth abundant metal which is giving a competition to lead.

http://mysite.du.edu/~jcalvert/phys/zinc.htm#Intr (1)

It is said that India is the first country where zinc named as metal in year 1374. In India contaminated zinc was taking from its native metal. It is not pure. It consists of a pink, water-insoluble powder consisting of zinc oxide and about 0.5 percent ferric oxide. Zinc ores and its searchers are found in different regions of India. They were working on new techniques to get zinc for the industrial usage between 12th to 16th centuries. Here medical industry used zinc as ayurverda known as Charaka Samhita. Around in 16th century the European come to know about zinc as before they were unknown although in India it is used since 13th century. First time zinc was found in UK, in 1743, at Bristol. China come to know about zinc little bit later of UK.

http://www.buzzle.com/articles/history-of-zinc.html

Source of Zinc

The largest source of zinc was found in Alaska, commonly known as Red Dog mine. The pure source of zinc was founding 1746. in 17th and 18th century when zinc was just discovered in Europe and they do not have as much zinc so for the applications Orient export the zinc to Europe. So because of this zinc was so costly for the European. Scientists were working to achieve zinc metal as possible low cost. And first time a German chemist Andreas S. Marggraf was able to extract zinc from its native materials. In its experiment zinc was isolating by means of heat from calamine and carbon. The idea about electrical properties of zinc was given by Galvani and Alessandro Volta in earlier

Properties

Value

Symbol

Zn

Atomic number

30

Atomic Mass

65.39

Group in periodic table

12

Period in periodic table

4

Block in periodic table

d-block

Standard state

Metal

Melting point

419.5°C

Boiling point

907°C

Color

bluish pale grey

Structure

hexagonal close packed

Electrical resistivity

6.16 μΩ-cm

Heat capacity

0.0925 cal/g-K

Coefficient of linear expansion

40.0 x 10-6per K

18th century. .

http://www.buzzle.com/articles/history-of-zinc.html

Specifications of Zinc:

http://www.elmhurst.edu/~chm/vchembook/102zinc.html

Zinc crystal structure

Here is some information about the crystal structure of zinc.

Space group: P63/mmc (Space group number: 194)

Structure: hcp (hexagonal close-packed)

Cell parameters:

a: 266.49 pm

b: 266.49 pm

c: 494.68 pm

α: 90.000°

β: 90.000°

http://www.webelements.com/zinc/crystal_structure.html

Isolation

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Now a day, there is abundance of zinc at commercial level so it is not mandatory to produce zinc in laboratory. For production zinc is obtained from sulphide ores. First at industrial plant zinc is heated in the oxygen environment so that oxide is formed (ZnO) then by reduction with form Zinc metal, but practically there is need a cleverly invented process which allow to produce oxide free zinc.

The chemical equations for the process are:

ZnO + C → Zn + CO

ZnO + CO → Zn + CO2

CO2 + C → 2CO

Electrolysis:

That is another process to obtain zinc. In this process ZnO is dissolved in sulphuric acid (H2SO4) results in zinc sulphate ZnSO4 in solution. In electrolysis of zinc the cathode is made up of aluminium and anode lead with some concentration of silver. The electrolyte process of zinc sulphate gives aluminium coated zinc metal. And anode has oxygen gas.100% pure zinc can be obtained from crude zinc. 99.9999% pure zinc obtained with technique single crystal growth (cholzaski or bridgeman technique). http://www.webelements.com/zinc/

Examples of Zinc Compounds

Zinc acetate

Zinc hydride

Zinc ammonium nitrite

Zinc nitrate

Zinc arsenate

Zinc oxide

Zinc chlorate

Zinc permanganate

Zinc chloride

Zinc phosphide, Zinc cyanide

Zinc sulfate

Zinc fluoride

http://www.scorecard.org/chemical-profiles/html/zinc.html

Chemistry of Zinc

The electron configuration of zinc is 1s22s22p63s23p63d104s2.

The valances of the zinc are +2. As a layer of thin sheet is formed on the upper side of pure zinc that's why it is inert for the water and diluted acids, if impurities like copper, platinum is present in zinc then it rapidly react with hydrogen. Hydrogen can also be obtained from the arsenical zinc. And its reduction potential is -0.76.

Fig: Electronic configuration of zinc

http://mysite.du.edu/~jcalvert/phys/zinc.htm#Chem (2)

Uses of Zinc

The principal uses for this metal are as follows:

For brass preparation (alloy).

Reaction of zinc with water or air results in impassible layer of zinc carbonate is formed on the zinc surface, which is very useful to prevent the iron to rust.

For the sheathing or roofing.

Zinc used as a precautionary material to avoid galvanic protection in steam boilers.

Zinc can be used as a protective element for the copper, brass and bronze.

Electric batteries have zinc plates.

When zinc react with oxygen and sulphuric acid, it results in formation of high grade White pain.

.http://chestofbooks.com/crafts/mechanics/Mechanical-Processes/17-Uses-Of-Zinc.html

History of Manganese

Manganese was discovered in 17th century. Before the discovery of the manganese people had idea about its compound. However a long time ago people were used minerals of the manganese, for example in Cave painting in which manganese were used before the discovery of the manganese. Pottery was very famous in ancestors of the Egyptians artisans. They used manganese for the shining and decoration of the ceramics. Egyptians and Romans were famous for the Glassmaking and they were used manganese for the glass either as removing agent or color to it.

Heather Hasan "understanding the element of the periodic table Manganese" 1st Edition (2008)

The history of the manganese name is yet unknown. A long time ago there was concept that manganese had two black minerals and had different gender (male and female) with different properties. But now a day they are known as magnes. Male magnes had ability to attract the iron. That's why iron magnetized and could be used as a magnet. Similarly the other gender worked opposite to the male gender and repelled iron but it was useful for removing the color of the glass. Latterly the female gender knew magnesia and in modern era called it pyrolusite or Mn2O3. Actually manganese and its minerals are not magnetic. With the mixing of two words manganese dioxide were also known as manganesum. This name given by glassmakers in 1600. Since there were two types of magnesia "negra" and "alba".

Negra is black ore of magnesia while alba is white ore and it is used in glass industry. These two different names are given by glassmakers and alchemists so that they were distinguishable. Manganese was taking from negra magnesia and experiment performed by a scientist Michele Mercati. He gave another name to negra magnesia "negra Manganesa. So there was no need to distinguish two ores of the magnesia by names that's why at that time magnesia Alba simply known as "magnesia", from which magnesium as a free element was taken much later.

Calvert,J.B.(2003-01-24)."Chromium and Manganese". <http://www.du.edu/~jcalvert/phys/chromang.htm. Retrieved 2009-04-30>.

In earlier of 19th century steel industry used manganese. It was seen that around in 1816, an alloy of manganese and iron made iron stronger, and if stress applied then it wouldn't broken.

Around the beginning of the 19th century, manganese was used in steelmaking and several patents were granted. In 1816, it was noted that adding manganese to iron made it harder, without making it any more brittle. In 1837, British academic James Couper noted an association between heavy exposures to manganese in mines with a form of Parkinson's Disease.

Couper, J. (1837). "On the effects of black oxide of manganese when inhaled into the lungs". Br. Ann. Med. Pharmacol. 1: 41-42.

From 19th century to present manganese phosphating electrochemical conversion is largely used for protection from rust and corrosion in USA.

In 1912, manganese phosphating electrochemical conversion coatings for protecting firearms against rust and corrosion were patented in the United States, and have seen widespread use ever since.

Olsen, Sverre E.; Tangstad, Merete; Lindstad, Tor (2007). "History of manganese". Production of Manganese Ferroalloys. Tapir Academic Press. pp. 11-12. ISBN 9788251921916.

Specifications of Manganese:

Properties

Value

Symbol

Mn

Atomic number

25

Atomic Mass

54.9380

Group in periodic table

7

Period in periodic table

4

Block in periodic table

d- block

Standard state

Solid at 298 K

Melting point

1523 K   (1250 oC)

Boiling point

2333 K   (2060 oC)

Color

gray-white

Structure

special: complex (cubic)

Electrical resistivity

Heat capacity

Coefficient of linear expansion

http://www.webelements.com/manganese/

Occurrence of manganese:

Around the world manganese occurrence number is 12 and it is a transition element. Its occurrence number in periodic table among transition element is 3. Manganese occurs in different forms in world and its occurrence percentage is about 0.106%. It has about 30 minerals out of which 12 are economically possible. The largest manganese source found in the South Africa and Ukraine (>80%). Manganese also found in the China, Australia, Brazil, Gabon, India, and Mexico.

Manganese is the 12th most abundant element and 3rd most abundant transition metal (cf. Fe, Ti). A number of forms of manganese occur in nature (~ 300 minerals) giving an overall abundance of 0.106%. 12 of these minerals are economically viable including: pyrolusite (MnO2), manganite (Mn2O3.H2O), hausmannite (Mn3O4) rhodochrosite (MnCO3) and Mn-nodules. The main deposits are found in South Africa and the Ukraine (> 80%) and other important manganese deposits are in China, Australia, Brazil, Gabon, India, and Mexico.

Extraction

For the extraction of metal a blast furnace is used, in which manganese containing alloy is reduced in the presence of Al. now metal behaves like iron react moderately at room temperature at highly reactive for non-metals at high temperature. Fro example when it reacts with nitrogen forms Mn3N2 and when burn in oxygen environment forms Mn3O4.

The metal is obtained by reduction with Al, or in a Blast furnace. The metal resembles iron in being moderately reactive and at high temperatures reacts vigorously with a range of non-metals. For example it burns in N2 at 1200 °C to form Mn3N2 and roasting in air gives Mn3O4.

http://wwwchem.uwimona.edu.jm/courses/manganese.html

Electronic configuration of Mn:

[Ar] 4s2 3d5;

If noble gas configuration is not used then - 1s2 2s2 2p6 3s2 3p6 4s2 3d5.

http://environmentalchemistry.com/yogi/periodic/Mn.html

Compounds of Manganese:

Manganese difluoride: MnF2

Manganese trifluoride: MnF3

Manganese tetrafluoride: MnF4

Manganese dichloride: MnCl2

Manganese trichloride: MnCl3

Manganese dichloride dihydrate: MnCl2.2H2O

Manganese dibromide: MnBr2

Manganese diiodide: MnI2

Manganese oxide: MnO

Manganese dioxide: MnO2

Dimanganese trioxide: Mn2O3

Dimanganese heptaoxide: Mn2O7

Trimanganese tetroxide: Mn3O4

Manganese sulphide: MnS

Manganese disulphide: MnS2

Manganese selenide: MnSe

Manganese telluride: MnTe

Tetramanganese hexdecacarbonyl: Mn4(CO)16

Dimanganese decacarbonyl: Mn2(CO)10

Manganese dibromide tetrahydrate: MnBr2.4H2O

Manganese dinitrate hexahydrate: Mn(NO3)2.6H2O

Tetraaquodiiodomanganese: MnI2.4H2O

Manganese dinitrate tetrahydrate: Mn(NO3)2.4H2O

Manganese dichloride: MnCl2.4H2O

http://www.amazon.com/exec/obidos/ASIN/0750633654/webelements

Uses

A large quantity of manganese is used in Alloys of different materials to produce ferromagnetic effect.

Euro coins are mostly made up of alloy nickel and copper but it is costly for 1 and 2 euro coins. As manganese occurs abundantly. That's why 1 and 2 euro coins made with manganese.

The cathodes of alkaline and dry cell batteries consist of oxides of manganese.

Manganese is a vital element of animal; it is used for the utilization of vitamin B1.

85-90% of the Manganese produced go in to the fabrication of ferromanganese alloys. The 1 and 2 Euro coins contain manganese since there it is more abundant and cheaper than nickel.

Manganese dioxide has been used in the cathodes of dry cell batteries and is used in newer alkaline batteries as well.

Manganese is widely distributed throughout the animal kingdom. It is an important trace element and may be essential for utilization of vitamin B1.

Zinc oxide (ZnO):

Zinc oxide is an inorganic compound and insoluble in water. It is in the form of powder which is largely used as a mixing material to make plastics, ceramics, glass, cement and car tires and lubricants etc. zinc oxide is found in the form of zincite and can be produced at the commercial level.

ZnO has semi conducting properties known in material science as II-VI compounds as in periodic table zinc is from 6th group and oxygen from 2nd group. It is widely used in device fabrication due to its very good properties such as good transparency, high electron mobility, wide bandgap, strong room-temperature luminescence, etc

Zinc oxide is an inorganic compound with the formula ZnO. It usually appears as a white powder, nearly insoluble in water. The powder is widely used as an additive into numerous materials and products including plastics, ceramics, glass, cement, rubber (e.g., car tires), lubricants paints, ointments, adhesives, sealants, pigments, foods (source of Zn nutrient), batteries, ferrites, fire retardants, first aid tapes, etc. ZnO is present in the Earth's crust as the mineral zincite; however, most ZnO used commercially is produced synthetically.

In materials science, ZnO is often called a II-VI semiconductor because zinc and oxygen belong to the 2nd and 6th groups of the periodic table, respectively. This semiconductor has several favorable properties: good transparency, high electron mobility, wide bandgap, strong room-temperature luminescence, etc. Those properties are already used in emerging applications for transparent electrodes in liquid crystal displays and in energy-saving or heat-protecting windows, and electronic applications of ZnO as thin-film transistors and light-emitting diodes are forthcoming as of 2009.

Hernandezbattez, A; Gonzalez, R; Viesca, J; Fernandez, J; Diazfernandez, J; MacHado, A; Chou, R; Riba, J (2008). "CuO, ZrO2 and ZnO nanoparticles as antiwear additive in oil lubricants". Wear 265: 422. doi:10.1016/j.wear.2007.11.013.

Origin and History

Zinc oxide or more commonly known in the art world as zinc white is one of the three white pigments -- lead, titanium and zinc -- used extensively for artistic and decorative paints. Although known since ancient times, zinc white apparently was not seriously considered an artists' pigment until after the 1850s. The widest application of the pure pigment has been in watercolors, sold under the name Chinese white, but is found often in mixtures with other pigments in oil and acrylic paints.

http://naturalpigments.com/detail.asp?PRODUCT_ID=475-31S

Physical properties:

Properties

Value

Molecular formula

ZnO

Molar mass

81.408 g/mol

Appearance

White solid

Odor

Odorless

Density

5.606 g/cm3

Melting point

1975 °C (decomposes)

Boiling point

2360 °C

Solubilityin

water0.16 mg/100 mL (30 °C)

Band gap

3.3 eV (direct)

Refractive index(nD)

2.0041

kahashi, Kiyoshi; Yoshikawa, Akihiko; Sandhu, Adarsh (2007). Wide bandgap semiconductors: fundamental properties and modern photonic and electronic devices

Crystal structure of Zinc Oxide:

Zinc oxide crystallizes in three forms: hexagonal wurtzite, cubic zincblende, and the rarely observed cubic rocksalt). The wurtzite structure is most stable at ambient conditions and thus most common. The zincblende form can be stabilized by growing ZnO on substrates with cubic lattice structure. In both cases, the zinc and oxide centers are tetrahedral.

Wurtzite:

The wurtzite crystal structure, named after the mineral wurtzite, is a crystal structure for various binary compounds. It is an example of a hexagonal crystal system.

The wurtzite structure is non-centrosymmetric (i.e., lacks inversion symmetry). Due to this, wurtzite crystals can (and generally do) have properties such as piezoelectricity and pyroelectricity, which centrosymmetric crystals lack.

Fig: wurtzite structure

http://en.wikipedia.org/wiki/Zinc_oxide#cite_note-ozgur-12

Rock salt:

Halite is the mineral form of sodium chloride, NaHYPERLINK "http://en.wikipedia.org/wiki/Chlorine"Cl, commonly known as rock salt. Halite forms isometric crystals. The mineral is typically colorless or white, but may also be light blue, dark blue, purple, pink, red, orange, yellow or gray depending on the amount and type of impurities. It commonly occurs with other evaporite deposit minerals such as several of the sulfates, halides, and borates.

Fig: cubic structure of Rock salt

Zincblende structure:

Another common structure is the "zincblende" structure (also spelled "zinc blende"), named after the mineral zincblende (sphalerite). As in the rock-salt structure, the two atom types form two interpenetrating face-centered cubic lattices. However, it differs from rock-salt structure in how the two lattices are positioned relative to one another. Altogether, the arrangement of atoms is the same as diamond cubic structure, but with alternating types of atoms at the different lattice sites

Fig: A zincblende unit cell

http://en.wikipedia.org/wiki/Cubic_crystal_system#Zincblende_structure

Chemical properties of ZnO:

ZnO occurs as white powder known as zinc white or as the mineral zincite. The mineral usually contains a certain amount of manganese and other elements and is of yellow to red color.

Klingshirn, C (2007). "ZnO: Material, Physics and Applications". ChemPhysChem 8 (6): 782.

Crystalline zinc oxide is thermochromic, changing from white to yellow when heated and in air reverting to white on cooling. This color change is caused by a very small loss of oxygen at high temperatures to form the non-stoichiometric Zn1+xO, where at 800 °C, x = 0.00007.

Wiberg, E. and Holleman, A. F. (2001). Inorganic Chemistry. Elsevier.

Zinc oxide is an amphoteric oxide. It is nearly insoluble in water and alcohol, but it is soluble in (degraded by) most acids, such as hydrochloric acid:

ZnO + 2 HCl → ZnCl2 + H2O

Bases also degrade the solid to give soluble zincates:

ZnO + 2 NaOH + H2O → Na2(Zn(OH)4)

ZnO reacts slowly with fatty acids in oils to produce the corresponding carboxylates, such as oleate or stearate. ZnO forms cement-like products when mixed with a strong aqueous solution of zinc chloride and these are best described as zinc hydroxy chlorides.

Nicholson, J. W; Nicholson, J. W (1998). "The chemistry of cements formed between zinc oxide and aqueous zinc chloride". Journal of Materials Science 33: 2251.

Electronic properties of ZnO

ZnO has a relatively large direct band gap of ~3.3 eV at room temperature; therefore, pure ZnO is colorless and transparent. Advantages associated with a large band gap include higher breakdown voltages, ability to sustain large electric fields, lower electronic noise, and high-temperature and high-power operation. The bandgap of ZnO can further be tuned from ~3-4 eV by its alloying with magnesium oxide or cadmium oxide.

Most ZnO has nHYPERLINK "http://en.wikipedia.org/wiki/N-type"-type character, even in the absence of intentional doping. Nonstoichiometry is typically the origin of n-type character, but the subject remains controversial. An alternative explanation has been proposed, based on theoretical calculations, that unintentional substitutional hydrogen impurities are responsible. Controllable n-type doping is easily achieved by substituting Zn with group-III elements such as Al, Ga, In or by substituting oxygen with group-VII elements chlorine or iodine.

Reliable p-type doping of ZnO remains difficult. This problem originates from low solubility of p-type dopants and their compensation by abundant n-type impurities. This problem is observed with GaN and ZnSe. Measurement of p-type in "intrinsically" n-type material is complicated by the inhomogeneity of samples.

Current limitations to p-doping does not limit electronic and optoelectronic applications of ZnO, which usually require junctions of n-type and p-type material. Known p-type dopants include group-I elements Li, Na, K; group-V elements N, P and As; as well as copper and silver. However, many of these form deep acceptors and do not produce significant p-type conduction at room temperature.

Electron mobility of ZnO strongly varies with temperature and has a maximum of ~2000 cm2/(V·s) at 80 K. Data on hole mobility are scarce with values in the range 5-30 cm2/(V·s).

http://en.wikipedia.org/wiki/Zinc_oxide

Production

Indirect (French) process

Metallic zinc is melted in a graphite crucible and vaporized at temperatures above 907 °C (typically around 1000 °C). Zinc vapor instantaneously reacts with the oxygen in the air to give ZnO, accompanied by a drop in its temperature and bright luminescence. Zinc oxide particles are transported into a cooling duct and collected in a bag house. This indirect method was popularized by LeClaire (France) in 1844 and therefore is commonly known as the French process. Its product normally consists of agglomerated zinc oxide particles with an average size of 0.1 to a few micrometers. By weight, most of the world's zinc oxide is manufactured via French process. Major applications involve industries related to rubber, varistors, sunscreens, paints, healthcare, and poultry nutrients. Recent developments involve acicular nanostructures (rods, wires, tripods, tetrapods, plates) synthesized using a modified French process known as catalyst-free combust-oxidized mesh (CFCOM) process. Acicular nanostructures usually have micrometre-length nanorods with nanometric diameters (below 100 nm).

Mahmud, Shahrom; Johar Abdullah, Mat; Putrus, Ghanim; Chong, John; Karim Mohamad, A. (2006). "Nanostructure of ZnO Fabricated via French Process and its Correlation to Electrical Properties of Semiconducting Varistors". Synthesis and Reactivity in Inorganic Metal-Organic and Nano-Metal Chemistry (formerly Synthesis and Reactivity in Inorganic and 36: 155. doi:10.1080/15533170500524462.

Direct (American) process

In the direct process, the starting material is various contaminated zinc composites, such as zinc ores or smeleter by-products. It is reduced by heating with a carbon additive (e.g. antracite) to produce zinc vapor, which is then oxidized as in the indirect process. Because of the lower purity of the source material, the final product is also of lower quality in the direct process as compared to the indirect one.

Laboratory synthesis

Fig: Synthetic ZnO crystals. Red and green color are associated with different concentrations of oxygen vacancies.[25]

A large number of ZnO production methods exist for producing ZnO for scientific studies and electronic applications. These methods can be classified by the resulting ZnO form (bulk, thin film, nanowire), temperature ("low", that is close to room temperature or "high", that is T ~ 1000 °C), process type (vapor deposition or growth from solution) and other parameters.

Large single crystals (many cubic centimeters) are usually grown by the gas transport (vapor-phase deposition), hydrothermal synthesis,[15]HYPERLINK "http://en.wikipedia.org/wiki/Zinc_oxide#cite_note-growth-24"[25]HYPERLINK "http://en.wikipedia.org/wiki/Zinc_oxide#cite_note-25"[26] or melt growth.[1] However, because of high vapor pressure of ZnO, growth from the melt is problematic. Growth by gas transport is difficult to control, leaving the hydrothermal method as a preference.[1] Thin films can be produced by chemical vapor deposition, metalorganic vapour phase epitaxy, electrodeposition, pulsed laser deposition, sputtering, sol-gel synthesis, spray pyrolysis, etc.

Zinc oxide may be produced in the laboratory by electrolyzing a solution of sodium bicarbonate with a zinc anode. Zinc hydroxide and hydrogen gas are produced. The zinc hydroxide upon heating decomposes to zinc oxide.

Zn + 2 H2O → Zn(OH)2 + H2

Zn(OH)2 → ZnO + H2O

Research papers

Application of ZnO:

Rubber

Activation

Acceleration

Biochemical Activity

Dielectric Strength

Heat Stabilization

Light Stabilization

Latex Gelation

Pigmentation

Reinforcement

Plastics

Ceramics

Pharmaceutical industry

Cosmetics

Adhesives, Mastics, Sealants

Photocopying

Lubricants

Paints

Metal - Protective Coatings

Sulfur removal

Foods and food-packaging materials

Fire retardants

Ferrites

Batteries, Fuel Cells, Photocells

Thermo elements

Silicate compositions

Fungicides

Portland cement

Spintronics

Piezoelectricity

Biosensor

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Application of zinc oxide nanostructures

As one of the important properties of ZnO, its piezoelectricity has been extensively studied for various applications in force sensing, acoustic wave resonator, acousto-optic modulator, etc. The piezoelectric property of ZnO nanostructures was also investigated for their potential applications in nano-electromechanical systems.

The fundamental study of the electrical properties of ZnO nanostructures is crucial for developing their future applications in nanoelectronics. Electrical transport measurements have been performed on individual ZnO nanowires and nanorods. Single ZnO nanowire was configured as field effect transistor (FET) following several procedures

The CVD grown ZnO nanostructures are single crystalline rendering them superior electrical property than polycrystalline thin film. For example, an electron field effect mobility of 7 cm2/V·s is regarded quite high for ZnO thin film transistors However, single crystalline ZnO nanowires show mobility as high as 80 cm2/V·s.35 And Park et al. had reported an electron mobility of 1000 cm2/Vs after coating the nanowires with polyimide to reduce the electron scattering and trapping at surface.

W. I. Park, J. S. Kim, G.-C. Yi, M. H. Bae, H.-J, Lee, Appl. Phys. Lett. 85, 5052 (2004).

The major impediment of ZnO for wide-ranging applications in electronics and photonics rests with the difficulty of p-type doping. Several p-type doping efforts have been reported, with a Ga and N codoping method, low resistivity (0.5 Ω·cm) p-type ZnO thin film was obtained. Successful p-type doping for ZnO nanostructures will greatly enhance their future applications in nanoscale electronics and optoelectronics.

P-type and n-type ZnO nanowires can serve as p-n junction diodes and light emitting diodes (LED). And field effect transistors (FET) fabricated from them can constitute complementary logic circuits. Combined with their optical cavity effect, electrically driven nanowire laser can be potentially implemented.

In addition to electrical transport studies, electric field emission from vertically-aligned

ZnO nanowire/nanorod has also been extensively investigated. Quasi-one-dimensional (Q1D) nanomaterial with sharp tip is a natural candidate for electron field emission. In fact, field emission from vertically-aligned ZnO nanoneedles and nanowires have been investigated by many groups.