Energy conversion efficiency in betavoltaic cells based on the diamond Schottky diode with a thin drift layer

This is a sel -a chi ed e sion o an o iginal a icle. This e sion may di e om he o iginal in pagina ion and ypog aphic de ails. Au ho (s): Ti le: Yea : Ve sion: Copy igh : Righ s: Righ s u l: Please ci e he o iginal e sion: CC BY-NC-ND 4.0 h ps://c ea i ecommons.o g/licenses/by-nc-nd/4.0/ Ene gy con e sion e iciency in be a ol aic cells based on he diamond Scho ky diode wi h a hin d i laye © Else ie L d. 2019 Accep ed e sion (Final d a ) G ushko, V.; Beliuskina, O.; Mamalis, A.; Lysako skiy, V.; Mi ske ich, E.; Ki ie , A.; Pe osyan, E.; Chaplynskyi, R.; Bezshyyko, O.; Lysenko, O. G ushko, V., Beliuskina, O., Mamalis, A., Lysako skiy, V., Mi ske ich, E., Ki ie , A., Pe osyan, E., Chaplynskyi, R., Bezshyyko, O., & Lysenko, O. (2020). Ene gy con e sion e iciency in be a ol aic cells based on he diamond Scho ky diode wi h a hin d i laye . Applied Radia ion and Iso opes, 157, A icle 109017. h ps://doi.o g/10.1016/j.ap adiso.2019.109017 2020 Jou nal P e-p oo Ene gy con e sion e iciency in be a ol aic cells based on he diamond Scho ky diode wi h a hin d i laye V. G ushko, O. Beliuskina, A. Mamalis, V. Lysako skiy, E. Mi ske ich, A. Ki ie , E. Pe osyan, R. Chaplynskyi, O. Bezshyyko, O. Lysenko PII: S0969-8043(19)30693-1 DOI: h ps://doi.o g/10.1016/j.ap adiso.2019.109017 Re e ence: ARI 109017 To appea in: Applied Radia ion and Iso opes Recei ed Da e: 16 June 2019 Re ised Da e: 26 No embe 2019 Accep ed Da e: 3 Decembe 2019 Please ci e his a icle as: G ushko, V., Beliuskina, O., Mamalis, A., Lysako skiy, V., Mi ske ich, E., Ki ie , A., Pe osyan, E., Chaplynskyi, R., Bezshyyko, O., Lysenko, O., Ene gy con e sion e iciency in be a ol aic cells based on he diamond Scho ky diode wi h a hin d i laye , Applied Radia ion and Iso opes (2020), doi: h ps://doi.o g/10.1016/j.ap adiso.2019.109017. This is a PDF ile o an a icle ha has unde gone enhancemen s a e accep ance, such as he addi ion o a co e page and me ada a, and o ma ing o eadabili y, bu i is no ye he de ini i e e sion o eco d. This e sion will unde go addi ional copyedi ing, ypese ing and e iew be o e i is published in i s inal o m, bu we a e p o iding his e sion o gi e ea ly isibili y o he a icle. Please no e ha , du ing he p oduc ion p ocess, e o s may be disco e ed which could a ec he con en , and all legal disclaime s ha apply o he jou nal pe ain. © 2019 Published by Else ie L d. CRediT au ho s a emen V G ushko: Concep ualiza ion, Fo mal analysis, W i ing- O iginal d a p epa a ion. O Beliuskina: Me hodology, W i ing- Re iewing and Edi ing. A Mamalis: W i ing- Re iewing and Edi ing. V Lysako skiy: Resou ces, In es iga ion, E Mi ske ich: So wa e, In es iga ion, A Ki ie : In es iga ion, Visualiza ion. E Pe osyan: Me hodology. R Chaplynskyi: Valida ion, Fo mal analysis. O Bezshyyko: Concep ualiza ion, Da a Cu a ion. O Lysenko: Supe ision. Ene gy con e sion e iciency in be a ol aic cells based on he diamond Scho ky diode wi h a hin d i laye V G ushko1, O Beliuskina2, A Mamalis3, V Lysako skiy1, E Mi ske ich1, A Ki ie 1,4, E Pe osyan5, R Chaplynskyi5, O Bezshyyko4and O Lysenko1 1V. Bakul Ins i u e o Supe ha d Ma e ials, 2, A oza odska , Kyi , 04074, Uk aine 2Depa men o Physics, Uni e si y o Jy ¨askyl¨a, Su on ie 9, FI 40014, Finland 3P ojec Cen e o Nano echnology and Ad anced Enginee ing (PC-NAE), NCSR “Demok i os”, A hens, 15310, G eece 4T. She chenko Na ional Uni e si y, 64/13, Volodymy ska, Kyi , 01601, Uk aine 5Ins i u e o Nuclea Resea ch, 47, Nauky A e, Kyi , 02000, Uk aine Abs ac The HPHT diamond Scho ky diode was assembled as a Me al/In insic/p- doped s uc u e be a ol aic cell (BC) wi h a e y hin (1 µm) d i laye and es ed unde 5 −30 keV elec on beam i adia ion using a scanning elec on mic oscope (SEM). The e ec o he β- adia ion ene gy and he backsca e ing o elec ons on he ene gy con e sion was s udied. F om he esul s ob ained, i is shown ha , he e iciency o he in es iga ed BC inc eases om 1.01 o 3.75 % wi h he dec ease o β-pa icle ene gy om 30 o 5 keV due o an inc ease o he elec on beam abso p ion in a hin d i laye . Maximum e iciency is achie ed when he elec on beam ene gy is close o he a e age β-decay ene gy o 3H. The BC maximum ou pu powe o he 1.6 µW was ob ained a an elec on beam ene gy o 15 keV, ha ma ches he β-decay ene gy o 63Ni. The o al BC con e sion e iciency a 15 keV elec on-beam ene gy is abou 3%. The calcula ions indica ed ha a p e e able β-sou ce o he diamond based BCs wi h a hin (1 µm) d i laye is 63Ni. Keywo ds: be a ol aic, diamond, ene gy con e sion e iciency, hin d i laye , Scho ky diode. P ep in submi ed o Applied Radia ion and Iso opes Decembe 7, 2019 1. In oduc ion The concep o using p-i-n and p-i-m (Scho ky) junc ions using o he be a- ol aic ene gy con e sion was p oposed in he 1950s (Rappapo (1954); P ann & Van Roosb oeck (1954)). Recen ly, nume ous be a ol aic cell (BC) de ices based on Si, SiC and GaN, we e de eloped (Bao e al. (2012); Zhang e al.5 (2018); Chand ashekha e al. (2006); Qiao e al. (2008); Ei ing e al. (2006)). No e ha , he be a ol aic de ices a e widely used in he ha sh adioac i e en- i onmen , like powe plan eac o s, spen nuclea uel s o ages e c., emo e places such as space and mine-like unde g ound, unde sea and so on. Mo eo e , hey a e mos no able o medical de ices such as pacemake s.10 Mos commonly used adioac i e sou ces o he indus ial BCs a e he 3H, 63Ni, 90S , 90Y, 147Pm, 35S, 33P, 204Tl, 85K iso opes (San e al. (2013); Sun e al. (2005); Lu e al. (2011); Yao e al. (2012); Chen e al. (2011); P eiss e al. (1957); Meie e al. (2009); Ei ing e al. (2006)). The ypical ou pu powe o he i ium BC is abou 120 nW. In he be a ol aic e ec s udies wi h 63Ni15 an induced cu en o ens o nanoamps o ew mic oamps was achie ed (San e al. (2013); Lu e al. (2011); Yao e al. (2012); Chen e al. (2011)). A u he de elopmen o long li e ime ene gy sou ces, based on β-iso opes o inc ease powe and educe size o BC, is ex emely challenging. Limi a ions o be a ol aic cells wi h a a ie y o be a sou ces had been s ud-20 ied ex ensi ely o e pas yea s. Fo example, Thei a anakul & P elas (2017) epo ed ha he be a ol aic e iciency o nuclea ba e ies based on silicon ca - bide be a ol aic cells wi h 3H, 63Ni, 35S, 147Pm, 90S and 90Y hin plana be a sou ces dec eases wi h inc easing be a ene gies. The 3H sou ce had he highes absolu e e iciency a 3.95% using he ull spec um ene gy dis ibu ion model.25 Oh e al. (2012) epo ed ha he calcula ed con e sion e iciencies we e limi ed o a ange o 0.013% o 2.02% o SiC-based be a ol aic cell wi h di e en be a sou ces. Acco ding o Zhang e al. (2018) he con e sion e iciency was in a ange o 3.74 −4.58% as he esul o he SiC PIN be a ol aic cell simula ion. Wu e al. (2011) p esen ed esul s on heo e ical s udy o silicon be a ol aic30 2 mic oba e y using 63Ni as be a sou ce wi h ob ained con e sion e iciency o 5%. Wu & Zhang (2019) in oduced he simula ion o con e sion e iciency o mul ilaye BC wi h silicon p-n junc ion con e e s and 63Ni sou ces. The o al con e sion e iciency o his BC limi ed o 3.3%. Mu phy e al. (2019) epo ed ha in he case o silicon diodes wi h h ee-dimensional ea u es when coupled35 wi h 147Pm oxide heo e ical e iciencies o 2.9 −5.8% can be achie ed. Mo e in o ma ion abou he BC epo ed e ec i eness can be ound in he e iew o nuclea ba e ies by P elas e al. (2014). The eliabili y and sa e y o BC, especially o medical applica ions, mainly depend on he adia ion ha dness and he mechanical s eng h o he semicon-40 duc ing ma e ial. Due o he high adia ion ole ance, he high mechanical s eng h and chemical ine ness diamond is an excellen ma e ial o be a ol aic de ices. Examples o BCs using diamonds a e p esen ed by Del au e e al. (2016), Bo masho e al. (2015), Ta elkin e al. (2016) and Zhao e al. (2017). I is no ed ha , he small ou pu powe o he diamond BCs limi s hei 45 use. The solu ion o his p oblem is o c ea e mul ilaye powe sou ces. In his case, he ou pu powe depends on he geome ical dimensions o he mul ilaye s uc u e and, he e o e, on he BC laye ’s hickness. Recen ly, a mul ilaye BC based on a diamond Scho ky diode wi h he he d i single laye cell size o 15 µm was p esen ed (Bo masho e al. (2018)). A50 educ ion o he hickness o he d i laye and, acco dingly, a dec ease in he size o a mul ilaye BC based on a diamond Scho ky diode, cons i u e he bes way o inc ease he powe densi y o such a de ice. The aim o ou esea ch was o s udy a be a ol aic ene gy con e sion e iciency in a diamond Scho ky diode wi h a d i laye hickness o 1 µm.55 2. Me hods and Ma e ials 2.1. The cu en gene a ion in he diamond Scho ky diode The ope a ion p inciple o he be a ol aic de ice is based on he elec on- hole pai gene a ion in a diamond Scho ky diode induced by β-pa icles emi ed 3 om adioac i e iso opes. The p ocess o elec on-hole pai s (EHP) gene a ion60 can be desc ibed by he gene a ion unc ion: g(x)∼exp(−αx) (Sachenko e al. (2015)), whe e, αis he linea elec on abso p ion coe icien and xis he dep h in diamond bulk. No e ha , only pa o he β-pa icle o al kine ic ene gy is abso bed in he d i laye wi h hickness o l= 1 µm, see Figu e 1(a). I is clea ly indica ed ha , he highe he pene a ing powe (i.e. longe s opping65 dep h) o he β- adia ion, he smalle his pa will be. The elec on-hole pai s induced by β- adia ion in a d i laye a e di ec ly con e ed in o an elec ic cu en o BC. Due o i s capabili y o e icien ly con e ing he ionizing adia ion in o an elec ic cu en , and, u he mo e, i s high adia ion ole ance, he mal conduc-70 i i y, mechanical s eng h and chemical ine ness, diamond was chosen as he main componen o he adioac i e powe sou ce. The diamond has a wide band gap and high dono and accep o ioniza ion ene gies. A oom empe a u e, as well as below i , he Fe mi le el is loca ed close o dono o accep o le els, de- pending on he concen a ion o impu i ies which is p edominan in he c ys al75 (Collins (2002)). The elec on-hole pai s o med inside he deple ion egion o he Scho ky diode a e sepa a ed by an in e nal elec ic ield, he eby o ming a adia ion-induced cu en in he BC (Manasse e al. (1976)). The Scho ky ba - ie heigh de ines he maximum ba e y ol age. This alue depends s ongly on he band gap s uc u e o he semiconduc o (Tung (2014)).80 I is known, ha a high concen a ion o a doping impu i y in a semiconduc- o leads o a hinning o he deple ion egion and, he eby, educes he numbe o he elec on-hole pai gene a ed in his egion (Bo masho e al. (2015)). The e o e, in diamond Scho ky diodes, he deple ion egion is ypically b oad- ened o a alue o 5 −10 µm a ze o bias by he o ma ion o an epi axial d i 85 laye on he su ace o a doped semiconduc o , in o which a small amoun o doping impu i y di uses. I is also known ha , he cha ge collec ion e iciency, Qo BC may d ama ically dec ease when a diode is i adia ed by high-ene gy elec ons which ha e highe pene a ing powe , because o he longe s opping dep h (Bo masho e al. (2015)).90 4 2.2. Expe imen al se up The schema ic diag am o a diamond Scho ky diode be a ol aic cell is shown in Figu e 1 (a). The p+subs a e o diamond diode was made om a bo on- doped single c ys al diamond g own by he empe a u e g adien me hod a high p essu e - high empe a u e (HPHT) (No iko e al. (2003)) wi h he bo on95 con en s o 1018 cm−3. Subsequen ly, diamond c ys al was cu as {001}planes and mechanically polished up o oughness o 2 nm RMS. The su ace quali y a e polishing was con olled by he Scanning Tunnelling Mic oscope (STM) echnique (G ushko e al. (2014); Lysenko e al. (2010)). Since a la ge numbe o s uc u al de ec s signi ican ly educes he li e ime o non-equilib ium ca ie s100 in a semiconduc o , wo sening, he e o e, he e iciency o be a ol aic ene gy con e sion, much a en ion was paid o he quali y o his bo on-doped pla e. Due o he la ge numbe o disloca ions, s acking aul s and win bounda ies in he {111}g ow h sec o s o he HPHT diamond (Chepugo e al. (2013)), mainly {001}and {311}sec o s we e used as a subs a e o he Scho ky junc ion.105 In o de o a oid he o ma ion o he ohmic con ac be ween he me al and he c ys al pla e and o inc ease he numbe o he elec on-hole pai s in he Scho ky junc ion egion he p−epi axial d i laye was deposi ed on he dia- mond pla e by he CVD me hod (Zhao e al. (2017)). The quali y o Scho ky junc ion subs a e su ace signi ican ly a ec s he quali y o he diamond epi-110 axial CVD laye . In ou case he hickness o he deposi ed CVD laye did no exceed 1 µm. The p esence o non-equilib ium ca ie s in he d i laye limi s he pen- e a ion dep h o he elec ic ield in he semiconduc o and, espec i ely, he dep h o he deple ion egion (Bo masho e al. (2015)). The hickness o he115 d i laye de e mines he Scho ky ba ie heigh and limi s he dep h o he deple ion egion whe e he induced cha ge is collec ed. Wi h an inc ease o he d i laye hickness om 100 o 500 nm, he heigh o he Scho ky ba ie inc ease om 1 o 1.8 eV (Zhao e al. (2017)). Acco ding o Bo masho e al. (2015) and Ta elkin e al. (2016), o a d i laye dep h o abou 10 µm and a120 ze o o se he dep h o he deple ion egion is abou 5 µm. 5 Figu e 1: (a) The schema ic diag am o a diamond Scho ky diode be a ol aic cell. The solid ma ke deno es elec ons and he open ma ke deno es holes, ~ε is he buil -in elec ic ield in he d i laye , l and W a e he d i laye ’s dep h and wid h, espec i ely. (b) The elec ic ci cui o he be a ol aic ene gy con e sion e iciency measu emen s. (c) The diamond be a ol aic cell p o o ype. A e he d i laye deposi ion, an Au laye wi h a hickness o 10 nm was deposi ed using he magne on spu e ing me hod in he A a mosphe e. The Au laye hickness was con olled by STM. On he backside o he diamond p+pla e, he Ti adhesi e laye , he Cu conduc ing laye and, inally, a hin125 Ag laye we e deposi ed by he same me hod. The spu e ing o Ti p o ided he o ma ion o a TiC in e laye on he diamond su ace and he s able ohmic con ac o he diamond pla e wi h a Cu/P conduc ing laye . The con e sion o β-decay ene gy in o elec ici y in a diamond Scho ky BC was in es iga ed using he Elec on Beam Induced Cu en (EBIC) echnique130 (Del au e e al. (2016)). Figu e 1 shows he elec ic ci cui used o he es ima- ion o he o al e iciency and he p o o ype o a diamond Scho ky diode BC based on he chip KD917A wi hou co e wa e . The diamond diode p+pla e is placed a he bo om o he chip, ha c ea es an ohmic con ac wi h a pai o uppe elec odes o he chip. Two bo om elec odes p o ide a con ac wi h135 he gold laye deposi ed on he op o he pla e. 6 s ops a beyond he d i laye (s opping dep h 1.5 −2µm, see Figu e 7(b)).240 The signi ican la e al sp ead o β-pa icles (la e al p ojec ion is abou 1.5 µm a he beam ene gy o 20 keV) leads o losses o β-pa icles a he edges o he d i laye . A u he inc ease o i adia ion ene gy leads o a u he dec ease o he a ea unde he in ensi y cu e and, as a esul , o he obse ed alue o he BC ou pu powe .245 The o al e iciency slowly sa u a es a he beam ene gy o 5 keV, see Figu e 4(b), appa en ly due o an inc ease o backsca e ing ( om 6% a 15 keV o 30% a 5 keV) and he beam ene gy losses ( om 0.8% a 15 keV o 6% a 5 keV) o he β- adia ion in a hin laye o gold on he su ace o he d i laye , see Figu e 5).250 0 200 400 600 800 1000 Dep h (nm) 0 1 2 3 4 EHP gene a ion in ensi y (pai /(s·nm)) ×1010 5 keV 10 keV 15 keV 20 keV 25 keV 30 keV Figu e 6: EHP gene a ion in ensi y as a unc ion o he pene a ion dep h o β-pa icles in he d i laye o BC unde di e en elec on beam ene gies. The dec ease o he o al con e sion e iciency wi h he beam ene gy inc ease, see Figu e 4(b), ag ees well wi h he obse ed small alue o he o al e iciency o high-ene gy β-pa icles (Bo masho e al. (2015)). Fo example, acco ding o Bo masho e al. (2015), o a mixed 90S −90Y sou ce wi h an a e age β-pa icle ene gy o abou 1.1 MeV (pene a ion dep h o abou 2 mm and deple ion255 egion o 5 µm), he measu ed alue o η= 0.004%, due o he ac ha only a small pa o he β-pa icles kine ic ene gy is abso bed in he Scho ky junc ion 13 −150 −100 −50 0 50 100 150 −200 −100 0 Dep h (nm) β=0.269 Au Diamond (a) −2000 −1000 0 1000 La e al axis (nm) −2000 −1000 0 Dep h (nm) β=0.065 (b) Figu e 7: T ajec o ies o β-pa icles in he BC and he backsca e ed coe icien βa a beam ene gy o 5 keV (a) and 20 keV (b). Backsca e ajec o ies a e ma ked in ed. deple ion egion and con e ed o elec ici y. Backsca e ing o β-pa icles in he diamond ma e ial is small (up o se e al pe cen ), due o a small a omic numbe o ca bon, compa ed o o he semicon-260 duc o ma e ials ( o example, Si 15% o GaN 25%) (Bo masho e al. (2015)), which helps o inc ease he o al e iciency coe icien η. 5. Conclusions F om he heo e ical and expe imen al s udies epo ed abo e, he ollowing concluding ema ks may be d awn:265 (a) The o al con e sion e iciency o he diamond Scho ky diode wi h a hin (1 µm) d i laye inc eases om abou 1% o 3.8% a he elec on beam ene gy dec ease om 30 keV o 5 keV, due o mo e e icien β- adia ion abso p ion by a hin d i laye a low beam ene gies. (b) The in luence o β-pa icle backsca e ing in he BC me allic coa ing on270 he o al con e sion e iciency a low (5 −15 keV) beam ene gies has o be aken in o accoun . (c) Acco ding o he Mon e Ca lo simula ions pe o med wi h CASINO so - wa e he pene a ion o β-pa icles in o he d i laye a ene gies g ea e han 14 15 keV exceeds 1 µm, which leads o a dec ease in he BC ou pu powe and275 he e iciency o a β-decay ene gy con e sion, since mos o he ajec o ies o β-pa icles go beyond he d i laye in which he cu en o BC is gene a ed. (d) La e al sp ead o β-pa icles a elec on beam ene gies g ea e han 20 keV exceeds 1.5 µm, which can lead o a signi ican loss o he ou pu powe and e iciency a he edges o he d i laye . This e ec can be signi ican o 280 mic o be a ol aic cells wi h a small a ea o d i laye wi h W <5µm. (e) The β- adia ion ene gy o 5 keV, a which he maximum ene gy con e - sion e iciency o abou 3.8 % is eached, is close o he a e age β-decay ene gy o 3H. The e o e, o ob ain he highes e iciency o he β-decay ene gy con e - sion in o elec ical ene gy 3H is he mos p e e ed sou ce o β- adia ion. Bu 285 he ou pu powe wi h such sou ce is jus ba ely o e 0.8 µW. ( ) The maximum ou pu powe (1.6 µW ) o BC was measu ed a an elec on beam ene gy o 15 keV, which is close o he β-decay ene gy o 63Ni, a he same ime he ene gy con e sion e iciency was high (abou 3 %). Thus, we can conclude ha 63 Ni is he mos p e e ed β-sou ce o he diamond be a ol aic290 cells based on a Scho ky diode wi h a hin d i laye . 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Diamond and ela ed ma e ials,73, 15–18. doi:10.1016/j.diamond.2016.11.005. 20 Highligh s  The o al con e sion e iciency o he diamond Scho ky diode wi h a hin (1µm) d i laye inc eases om abou 1 o 3.8 % while he elec on beam ene gy dec ease om 30 keV o 5 keV due o he inc ease in he adso p ion o be a pa icles by a hin d i laye .  The mos p e e ed be a sou ce o he diamond Scho ky diode wi h a hin d i laye is 63Ni.  The β-pa icles backsca e ed coefficien and he beam ene gy loss in he Scho ky con ac signi ican ly a ec s he o al con e sion e iciency o he diamond Scho ky diode a low (5 -15 keV) beam ene gies.  The la e al elec on sp ead exceeds 1.5 µm a beam ene gies g ea e han 20 keV, which can lead o a significan loss o he ou pu powe and efficiency a he edges o he d i laye . This effec can be significan o mic o be a ol aic cells wi h a small (<25 µm2) a ea o a d i laye . Decla a ion o in e es s ☒ The au ho s decla e ha hey ha e no known compe ing inancial in e es s o pe sonal ela ionships ha could ha e appea ed o in luence he wo k epo ed in his pape . ☐The au ho s decla e he ollowing inancial in e es s/pe sonal ela ionships which may be conside ed as po en ial compe ing in e es s: