Editing Germanium (section)

== Applications ==
The major global end uses for germanium were electronics and solar applications, fiber-optic systems, infrared optics, and polymerization catalysts. Other uses included chemotherapy, metallurgy, and phosphors.<ref>{{Cite web |last=Mineral |first=Commodity |date=January 4, 2024 |title=Mineral Commodity Summaries 2024 |url=https://pubs.usgs.gov/periodicals/mcs2024/mcs2024-germanium.pdf |access-date=May 14, 2025 |website=Mineral Commodity}}</ref>

=== Optics ===
[[File:Singlemode fibre structure.svg|thumb|right|upright=.65|alt=A drawing of four concentric cylinders.|A typical single-mode optical fiber. Germanium oxide is a [[dopant]] of the core silica (Item 1). {{olist
    |Core 8&nbsp;µm
    |Cladding 125&nbsp;µm
    |Buffer 250&nbsp;µm
    |Jacket 400&nbsp;µm
}}]]
The notable properties of [[Germanium dioxide|germania]] (GeO<sub>2</sub>) are its high [[refractive index|index of refraction]] and its low [[Dispersion (optics)|optical dispersion]]. These make it especially useful for [[wide-angle camera lens]]es, [[microscopy]], and the core part of [[optical fiber]]s.<ref>{{cite journal |title=Infrared Detector Arrays for Astronomy |journal=Annual Review of Astronomy and Astrophysics |date=2007 |doi=10.1146/annurev.astro.44.051905.092436 |last=Rieke |first=G. H. |s2cid=26285029 |volume=45 |issue=1 |pages=77–115 |bibcode=2007ARA&A..45...77R}}</ref><ref name="Brown">{{cite web |url=http://minerals.usgs.gov/minerals/pubs/commodity/germanium/220400.pdf |title=Germanium |first=Robert D. Jr. |last=Brown |publisher=U.S. Geological Survey |year=2000 |access-date=2008-09-22 |archive-date=2011-06-08 |archive-url=https://web.archive.org/web/20110608071221/http://minerals.usgs.gov/minerals/pubs/commodity/germanium/220400.pdf |url-status=live}}</ref> It has replaced [[titanium dioxide|titania]] as the [[dopant]] for silica fiber, eliminating the subsequent heat treatment that made the fibers brittle.<ref>{{cite web |url=http://ptgmedia.pearsoncmg.com/images/1587051052/samplechapter/1587051052content.pdf |title=Chapter III: Optical Fiber For Communications |publisher=Stanford Research Institute |access-date=2008-08-22 |archive-date=2014-12-05 |archive-url=https://web.archive.org/web/20141205210827/http://ptgmedia.pearsoncmg.com/images/1587051052/samplechapter/1587051052content.pdf |url-status=live}}</ref> At the end of 2002, the fiber optics industry consumed 60% of the annual germanium use in the United States, but this is less than 10% of worldwide consumption.<ref name="Brown" /> [[GeSbTe]] is a [[phase change material]] used for its optic properties, such as that used in [[DVD-RW|rewritable DVDs]].<ref>{{cite web |url=http://www.osta.org/technology/pdf/dvdqa.pdf |archive-url=https://web.archive.org/web/20090419202545/http://www.osta.org/technology/pdf/dvdqa.pdf |archive-date=2009-04-19 |title=Understanding Recordable & Rewritable DVD |edition=First |access-date=2008-09-22 |publisher=Optical Storage Technology Association (OSTA)}}</ref>

Because germanium is transparent in the infrared wavelengths, it is an important [[infrared]] optical material that can be readily cut and polished into lenses and windows. It is especially used as the front optic in [[Thermographic camera|thermal imaging cameras]] working in the 8 to 14&nbsp;[[micrometre|micron]] range for passive thermal imaging and for hot-spot detection in military, mobile [[night vision]], and fire fighting applications.<ref name="Moska" /> It is used in infrared [[spectroscope]]s and other optical equipment that require extremely sensitive [[thermography|infrared detectors]].<ref name="Brown" /> It has a very high [[refractive index]] (4.0) and must be coated with anti-reflection agents. Particularly, a very hard special antireflection coating of [[diamond-like carbon]] (DLC), refractive index 2.0, is a good match and produces a diamond-hard surface that can withstand much environmental abuse.<ref>{{cite journal |first=Alan H. |last=Lettington |doi=10.1016/S0008-6223(98)00062-1 |title=Applications of diamond-like carbon thin films |volume=36 |issue=5–6 |date=1998 |pages=555–560 |journal=Carbon |bibcode=1998Carbo..36..555L}}</ref><ref>{{cite journal |first=Michael N. |last=Gardos |author2=Bonnie L. Soriano |author3=Steven H. Propst |title=Study on correlating rain erosion resistance with sliding abrasion resistance of DLC on germanium |journal=Proc. SPIE |volume=1325 |page=99 |date=1990 |doi=10.1117/12.22449 |issue=Mechanical Properties |series=SPIE Proceedings |editor1-last=Feldman |editor1-first=Albert |editor2-last=Holly |editor2-first=Sandor |bibcode=1990SPIE.1325...99G |s2cid=137425193}}</ref>

=== Electronics ===
Germanium can be alloyed with [[silicon]], and [[silicon–germanium]] alloys are rapidly becoming an important semiconductor material for high-speed integrated circuits. Circuits using the properties of Si-SiGe [[heterojunction]]s can be much faster than those using silicon alone.<ref>{{cite journal |doi=10.1109/TED.2003.810484 |title=SiGe HBT and BiCMOS technologies for optical transmission and wireless communication systems |date=2003 |last=Washio |first=K. |journal=IEEE Transactions on Electron Devices |volume=50 |issue=3 |pages=656–668 |bibcode=2003ITED...50..656W}}</ref> The SiGe chips, with high-speed properties, can be made with low-cost, well-established production techniques of the [[silicon chip]] industry.<ref name="usgs" />

High efficiency [[solar panel]]s are a major use of germanium. Because germanium and [[gallium arsenide]] have nearly identical [[lattice constant]], germanium substrates can be used to make gallium-arsenide [[solar cell]]s.<ref>{{cite journal |doi=10.1002/pip.446 |title=Space and terrestrial photovoltaics: synergy and diversity |date=2002 |last1=Bailey |first1=Sheila G. |journal=Progress in Photovoltaics: Research and Applications |volume=10 |issue=6 |pages=399–406 |last2=Raffaelle |first2=Ryne |last3=Emery |first3=Keith |hdl=2060/20030000611 |bibcode=2002sprt.conf..202B |s2cid=98370426 |hdl-access=free}}</ref> Germanium is the substrate of the wafers for high-efficiency [[multijunction photovoltaic cell]]s for space applications, such as the [[Mars Exploration Rover]]s, which use triple-junction gallium arsenide on germanium cells.<ref>{{cite journal |doi=10.1016/S0094-5765(02)00287-4 |title=The performance of gallium arsenide/germanium solar cells at the Martian surface |date=January 2004 |first=D. |last=Crisp |author2=Pathare, A. |author3=Ewell, R. C. |journal=Acta Astronautica |volume=54 |issue=2 |pages=83–101 |bibcode=2004AcAau..54...83C}}</ref> High-brightness LEDs, used for automobile headlights and to backlight LCD screens, are also an important application.<ref name="usgs" />

Germanium-on-insulator (GeOI) substrates are seen as a potential replacement for silicon on miniaturized chips.<ref name="usgs" /> CMOS circuit based on GeOI substrates has been reported recently.<ref>{{cite journal |first1=Heng |last1=Wu |first2=Peide D. |last2=Ye |date=August 2016 |title=Fully Depleted Ge CMOS Devices and Logic Circuits on Si |journal=[[IEEE Transactions on Electron Devices]] |volume=63 |issue=8 |pages=3028–3035 |doi=10.1109/TED.2016.2581203 |bibcode=2016ITED...63.3028W |s2cid=3231511 |url=https://engineering.purdue.edu/~yep/Papers/TED_Ge%20Fully%20Depleted%20CMOS_2016.pdf |access-date=2019-03-04 |archive-date=2019-03-06 |archive-url=https://web.archive.org/web/20190306044456/https://engineering.purdue.edu/~yep/Papers/TED_Ge%20Fully%20Depleted%20CMOS_2016.pdf |url-status=live}}</ref> Other uses in electronics include [[phosphor]]s in [[fluorescent lamp]]s<ref name="lanl" /> and solid-state light-emitting diodes (LEDs).<ref name="usgs" /> Germanium transistors are still used in some [[effects pedal]]s by musicians who wish to reproduce the distinctive tonal character of the [[Distortion (music)|"fuzz"-tone]] from the early [[rock and roll]] era, most notably the [[Fuzz Face|Dallas Arbiter Fuzz Face]].<ref>{{cite journal |author=Szweda, Roy |date=2005 |title=Germanium phoenix |journal=[[III-Vs Review]] |volume=18 |issue=7 |page=55 |doi=10.1016/S0961-1290(05)71310-7}}</ref>

Germanium has been studied as a potential material for implantable bioelectronic sensors that are [[Biodegradable electronics|resorbed]] in the body without generating harmful hydrogen gas, replacing [[zinc oxide]]- and [[indium gallium zinc oxide]]-based implementations.<ref>{{ cite journal |last1=Zhao |first1=H. |last2=Xue |first2=Z. |last3=Wu |first3=X. |display-authors=2 |date=21 July 2022 |title=Biodegradable germanium electronics for integrated biosensing of physiological signals. |journal=npj Flexible Electronics |volume=6 |at=63 |doi=10.1038/s41528-022-00196-2 |s2cid=250702946 |doi-access=free}}</ref>

Germanium was also used to create many of the circuits found in some of the very first pieces of electronic musical gear, initially 1950s, primarily in early transistor-based circuits. The first guitar effects pedals in the 1960s – Fuzz pedals like the Maestro FZ-1 (1962), Dallas-Arbiter Fuzz Face (1966), and Tone Bender (1965) - used germanium transistors.<ref>{{Cite web |last=joe |date=2012-01-03 |title=The Germanium Mystique |url=https://tonefiend.com/diy/the-germanium-mystique/ |access-date=2025-02-21 |website=tonefiend.com |language=en-US}}</ref> Silicon diodes are more frequently used in more modern equipment, but germanium diodes are still used in some applications as they have lower barrier potential and smoother [[transconductance]] curves, leading to less harsh [[Clipping (audio)|clipping]].<ref>{{Citation |last=Dailey |first=Denton J. |title=Guitar Effects Circuits |date=2013 |work=Electronics for Guitarists |pages=199–200 |url=https://link.springer.com/chapter/10.1007/978-1-4614-4087-1_5 |access-date=2025-02-21 |place=New York, NY |publisher=Springer New York |language=en |doi=10.1007/978-1-4614-4087-1_5 |isbn=978-1-4614-4086-4}}</ref>

=== Other uses ===
[[File:Pet Flasche.JPG|thumb|upright|A [[polyethylene terephthalate|PET]] [[bottle]]|alt=Photo of a standard transparent plastic bottle.]]
Germanium dioxide is also used in [[catalyst]]s for [[polymerization]] in the production of [[polyethylene terephthalate]] (PET).<ref name="Thiele">{{cite journal |last=Thiele |first=Ulrich K. |date=2001 |title=The Current Status of Catalysis and Catalyst Development for the Industrial Process of Poly(ethylene terephthalate) Polycondensation |journal=International Journal of Polymeric Materials |volume=50 |issue=3 |pages=387–394 |doi=10.1080/00914030108035115 |s2cid=98758568}}</ref> The high brilliance of this polyester is especially favored for PET bottles marketed in Japan.<ref name="Thiele" /> In the United States, germanium is not used for polymerization catalysts.<ref name="usgs" />

Due to the similarity between silica (SiO<sub>2</sub>) and germanium dioxide (GeO<sub>2</sub>), the silica stationary phase in some [[gas chromatography]] columns can be replaced by GeO<sub>2</sub>.<ref>{{cite journal |title=Germania-Based, Sol-Gel Hybrid Organic-Inorganic Coatings for Capillary Microextraction and Gas Chromatography |last1=Fang |first1=Li |last2=Kulkarni |first2=Sameer |last3=Alhooshani |first3=Khalid |last4=Malik |first4=Abdul |journal=Anal. Chem. |volume=79 |issue=24 |pages=9441–9451 |date=2007 |doi=10.1021/ac071056f |pmid=17994707}}</ref>

In recent years germanium has seen increasing use in precious metal alloys. In [[sterling silver]] alloys, for instance, it reduces [[firescale]], increases tarnish resistance, and improves precipitation hardening. A tarnish-proof silver alloy trademarked [[Argentium sterling silver|Argentium]] contains 1.2% germanium.<ref name="usgs" />

[[Semiconductor detector#Germanium detectors|Semiconductor detectors]] made of single crystal high-purity germanium can precisely identify radiation sources—for example in airport security.<ref>{{cite web |title=Performance of Light-Weight, Battery-Operated, High Purity Germanium Detectors for Field Use |first1=Ronald |last1=Keyser |last2=Twomey |first2=Timothy |last3=Upp |first3=Daniel |url=http://www.ortec-online.com/papers/inmm_2003_keyser.pdf |access-date=2008-09-06 |publisher=Oak Ridge Technical Enterprise Corporation (ORTEC) |archive-url=https://web.archive.org/web/20071026162911/http://www.ortec-online.com/papers/inmm_2003_keyser.pdf |archive-date=October 26, 2007 |url-status=dead}}</ref> Germanium is useful for [[Crystal monochromator|monochromators]] for [[beamline]]s used in [[single crystal]] [[neutron scattering]] and [[Synchrotron light|synchrotron X-ray]] diffraction. The reflectivity has advantages over silicon in neutron and [[High energy X-rays|high energy X-ray]] applications.<ref>{{cite journal |doi=10.1142/S0218301396000062 |date=1996 |journal=International Journal of Modern Physics E |volume=5 |issue=1 |pages=131–151 |title=Optimization of Germanium for Neutron Diffractometers |bibcode=1996IJMPE...5..131A |last1=Ahmed |first1=F. U. |last2=Yunus |first2=S. M. |last3=Kamal |first3=I. |last4=Begum |first4=S. |last5=Khan |first5=Aysha A. |last6=Ahsan |first6=M. H. |last7=Ahmad |first7=A. A. Z.}}</ref> Crystals of high purity germanium are used in detectors for [[gamma spectroscopy]] and the search for [[dark matter]].<ref>{{cite journal |doi=10.1016/j.nuclphysa.2005.02.155 |title=Astrophysical constraints from gamma-ray spectroscopy |date=2006 |last1=Diehl |first1=R. |journal=Nuclear Physics A |volume=777 |issue=2006 |pages=70–97 |last2=Prantzos |first2=N. |last3=Vonballmoos |first3=P. |arxiv=astro-ph/0502324 |bibcode=2006NuPhA.777...70D |citeseerx=10.1.1.256.9318 |s2cid=2360391}}</ref> Germanium crystals are also used in X-ray spectrometers for the determination of phosphorus, chlorine and sulfur.<ref>Eugene P. Bertin (1970). ''Principles and practice of X-ray spectrometric analysis'', Chapter 5.4 – Analyzer crystals, Table 5.1, p. 123; Plenum Press</ref>

Germanium is emerging as an important material for [[spintronics]] and spin-based [[quantum computing]] applications. In 2010, researchers demonstrated room temperature spin transport<ref>{{Cite journal |last1=Shen |first1=C. |last2=Trypiniotis |first2=T. |last3=Lee |first3=K. Y. |last4=Holmes |first4=S. N. |last5=Mansell |first5=R. |last6=Husain |first6=M. |last7=Shah |first7=V. |last8=Li |first8=X. V. |last9=Kurebayashi |first9=H. |date=2010-10-18 |title=Spin transport in germanium at room temperature |journal=Applied Physics Letters |volume=97 |issue=16 |page=162104 |doi=10.1063/1.3505337 |issn=0003-6951 |bibcode=2010ApPhL..97p2104S |url=https://eprints.soton.ac.uk/271616/1/Gespin.pdf |access-date=2018-11-16 |archive-date=2017-09-22 |archive-url=https://web.archive.org/web/20170922180043/https://eprints.soton.ac.uk/271616/1/Gespin.pdf |url-status=live}}</ref> and more recently donor electron spins in germanium has been shown to have very long [[coherence time]]s.<ref>{{Cite journal |last1=Sigillito |first1=A. J. |last2=Jock |first2=R. M. |last3=Tyryshkin |first3=A. M. |last4=Beeman |first4=J. W. |last5=Haller |first5=E. E. |last6=Itoh |first6=K. M. |last7=Lyon |first7=S. A. |date=2015-12-07 |title=Electron Spin Coherence of Shallow Donors in Natural and Isotopically Enriched Germanium |journal=Physical Review Letters |volume=115 |issue=24 |pages=247601 |doi=10.1103/PhysRevLett.115.247601 |pmid=26705654 |arxiv=1506.05767 |bibcode=2015PhRvL.115x7601S |s2cid=13299377}}</ref>