Nimnoqilho

Nimnoqilho guruhi kaloni moddaho (sakht, moe, amorfi), ki az rui qimati noqiliyati elektriashon (a) bayni metallho (o — 10e — 104 Om—1 santimetr-1) va dielektrikho (o < s 10-1°—Yu-12 Om-1 om-1) joy megirand (qimathoi o ba harorati khona muvofiqand). Jihati az metallho farqkunandai Nimnoqilho in ast, ki bo afzoishi harorat noqiliyati elektrii onho ziyod meshavad. Zero bo afzoishi harorat harakati garmi bandhoi elektroniro mekanad va yak qismi elektronho ba homiloni ozodi jarayon tabdil meyoband. Bandhoi elektroni na faqat az tasiri harorat, balki az tasiri rushnoi, se­li zarradoi sare, maydoni elekt­rii zur va gayra niz kanda meshavand. Ba hamin sabab noqiliyati elektrii Nimnoqilho ba tasiroti beruna, inchunin ba mavjudiyati gashho va nuqsonho dar kristall khele hasoos meboshad.

Binobar in bo rohi tagyir dodani harorat, dokhil namudani gashho va gayra noqiliyati elektrii Nimnoqilro dar khu­dudhoi vase idora kardan mumkin ast. Az in ru, agar Nimnoqilro ba guruhi alohida judo nakarda, dar borai holati nimnoqilii moddahoi gayrimetalli sukhan merondem, aniqu khubtar mebud. Ammo chun Nimnoqil beshtar majmui yakchand guruhhoi makhsusi moddahoero qabul mekunand, ki khususiyati nimnoqiliashon dar harorati khona (300 K) ham ravshan zuhur meyoband. Masalan, ele­menthoi guruhi IV sistemai davrii elementhoi khimiyavii Mendeleev (Ge, Si); payvasthoi elementhoi gurukhi III (AI, Sa, In) va elementhoi guruhi V (R, As, Sb), ki Nimnoqilhoi navi Ain BV (GaAs, InSb, GaP, 1pRva gayra) nom giriftaand; elementhoi guruhi VI va V (Te, Se, As, Sb, Bi) ; payvast­khoi navi A»VBVi( PbS, PbTe, SnTe, GeTe va g.); payvasthoi gurukhi VI va metallkhoi nodir (Ti, V, Mn, Fe,Hi, Sm, Eu va g.); Nimnoqilhoi organiki va gayra.  Azbaski dar jismi sakht atomho yo ionho to masofai taqriban barobari radiusi atom ba ham nazdik mesha­vand, elektronhoi valenti az yak atom ba atomi digar guzashta metavonand.

Chunin mubodilai elektronho bandi kovalentiro ba vujud meovarad. In manzara ba Ge, ki yake az Nimnouilhoi muqarrarist, tatbiqpazir ast. Hamai atomhoi Ge neytraliand va bo bandi kovalenti ba ham aloqamandand. Ammo mubodilai elektronho dar bayni atomho bevosita noqiliyati elektriro ba amal nameorad, zero umuman taqsimoti zichii elektroni qatiyan muqarrar meboshad; ba har yak bandi bayni jufti atomhoi hamsoya 2-toi elektron muvofiq meoyad. Baroi dar chunin kristall ba     vujud ovardani noqiliyat. kandani aqalan yake az bandho lozim ast (bo rohi garmkuni, furuburdi fotonho va gayra), yane elektronro az in band raho namuda, onro ba yacheykai digari kristall kuchondan lozim ast, dar joi nav in elektron ziyodati khohad bud. Chunin elektron minbad az yak yacheykai kristall ba yacheykai digar ozod harakat karda metavonad (zero baroi on hamai yacheykaho ekvivalentand). Azbaski in elekt­ron dar tamomi kristall ziyodati khohad bud, on zaryadi manfii barziyodro bo khud mebarad, yane bo elektroni noqiliyat tabdil meyobad.

Bandi kandashuda ba surokhi dar sarosari kristall sayrkunanda tabdil meyobad, zero dar mavridi mubodilai zur elektroni yake az bandhoi hamsoya darhol joi kholishudai bandro ishgol karda, dar navbati khud «surokhi» navro hosil mekunad. Norasoii elektroni yake az bandho dar atom (yo khud chufti atom­ho) ba vuchud omadani yak vohid za­ryadi musbatro mefahmonad, ki on guyo yakchoya bo surokh az yak qismi kristall ba qismi digarash mekuchad.

Noqiliyati elektrii Nimnoqilhoro ham elektronhoi atomhoi khudi moddai dodashuda (noqiliyati khususi), ham elektronhoi atomhoi gash (noki­liyati gashi) ba vujud ovarda metavonand. Dar barobari in nuqsonhoi gunoguni strukturai kris­tall, mamalan, vakansiyaho, atomhoi bay­ni girehhoi pancharai kristall, inchunin norasoi yo barziyodii atomhoi yake az komponenthoi payvasthoi nimnoqili (masalan, norasoii. Ni dar NiO yo S dar PbS) niz manbai homiloni jarayon meboshand.

Gashho va nuqsonhoro ba donorho va akseptorho chudo mekunand. Donordo ba hachmi Nimnoqilho elektronhoi barziyod doda, noqiliyati elekt­ron i (noqiliyati navi p, az lotini negative — manfi), akseptorho boshand, elektronhoi valentii moddaero, ki ba on dokhil karda shudaand, zabt karda, surokhho va dar natija in noqiliyati surokhi (noqplpyati navi r, az lotini positive — musbat) ba vujud meorand. Hamchun misoli donorho gashatomhoi elementhoi guruhi V (R, As, Sb)-po dar Ge va Si nom burdan mumkin ast. In guna gashatom dar panjarai kristalli joygir shuda, dar yake az yacheykahoi on joi atomi Gc-po ishgol mekunad. Dar in vaqt az 5-to elektronhoi va­lentii on 4-toash bo hamsoyaatomhoi Ge bandi kovalenti tashkil mekunand, elektroni 5-um boshad, baroi panjarai dodashuda «ziyodati» meshavad, zero hamai bandho allakay pur shudaand. In elektron, kn dar hej yak yacheykai elementarii panjarai kristalli «muqimi» shuda nametavonad, ba elektroni noqiliyat tabdil meyobad.

Aynan hamin tavr, atomhoi elementhoi guruhi III (V, Al, Ga, In) dar Ge va Si misoli akseptorho meboshand. In akseptorho bar zammi 3 elektroni valentin khud yake ae elektronhoi valentii Ge-po zabt karda, bo hamsoyaatomhoi nazdiktarini Ge 4-to bandi kovalenti hosil menamoyand va ba ionhoi manfii za­ryadnok mubaddal meshavand. Dar joi elektroni zabtshuda surokh boqi memonad, ki on hangomi harorathoi na  on qadar past dar sarosari kris­tall ozod joy ivaz karda metavonad.

Garchande, ki Nimnoqilho hamchun guruhi makhsusi materialho dar okhiri asri 19 malum budand, faqat inkishofi nazariyai kvanti ba fahmidani khususiyathoi dielektrho, Nimnoqilho va metallho (Uilson, ShMA, 19E1) imkoniyat dod. Chunin khosiyathoi asosii Nimnoqilho, ba monandi rostshavii jarayon dar joi bahamrasii metall — Nimnoqil, fotonoqiliyat va gayra az in ham peshtar oshkor va dar asosi onhr asbobhoi avvalin sokhta shudand. O. V. Losev imkonpazirii baroi taqviyat va generatsiyai lappishho istifoda burdani kontakthoi nimnoqili (detektorhoi kristalli)-ro isbot kard, ki minbad joi onhoro lampahoi elektro­ni va tranzistorho ishgol namudand. Avvali solhoi 50 asri 20 tadqiqi puranji fizikai Nimnoqilho cap shud, ki ba on mu- vaffaqiyathoi dar sohai tekhnologiyai sofkoriyu legironii kristallho ba dastomada musoidat kardand. Vobasta ba kashfi afkanishoti majburi dar GaAs (D. N. Nasledov, A. A. Rogachyov, S. M. Rivkin, B. V. Sarenkov, SSSR, 1962) diqqati tadkikitchiyonro khosiyathoi optikii Nimnoqilho jalb namud, ki on ba bunyodi lazerhoi nimnoqili [Kholl (ShMA), B. M. Vul, A. P. Shotov, J. I. Alfyorov va digar (SSSR)] ovarda rasond.

Tadqiqoti vasei Nimnoqilho dar SSSR tahti rohbarii A. F. Ioffe dar Instituti fizika va tekhnikai Akademiyai Fanhoi SSSR oxiri solhoi 20 cap shud. Aksari mafhumhoi  nazariyavii Nimnoqilhopo bori avval Ya. I. Frenkel, I. B. Tamm, B. I. Davi­dov, E. F. Gross, V. A. Juze, V. E.Latakaryov, V. M. Tuchkevich va digar tashakkul dodand. Dar Tojikiston ba tadqiqoti sohai Nimnoqilho kormandoni Instituti fizika va tekhnikai Akademiyai Fanhoi RSS Tojikiston mashguland.

Adabiyot: Ioffe A. F., Fizika polupro­vodnikom, Moskva— Leningrad.      1957; Anselm A. I., Vvedenie v teoriyu poluprovodni­kov, Moskva 1978; Kireev P. S., Fizika poluprovodnikov, 2 izdanie., 1975; Gut­man F., L a y o n s L., Organicheskie po­luprovodniki, perevod s angliyskogo, 1970. Sh. Mavlonov.