Nanoscale memristive radiofrequency switches

Transcription

1 University of Msshusetts Amherst From the SeletedWorks of Qingfei Xi 1 Nnosle memristive rdiofrequeny swithes Shung Pi Mohmmd Ghdiri-Sdrdi Joseph C. Brdin Qingfei Xi Aville t:

2 ARTICLE Reeived Aug 1 Aepted 1 My 1 Pulished Jun 1 DOI: 1.1/nomms19 Nnosle memristive rdiofrequeny swithes Shung Pi 1, Mohmmd Ghdiri-Sdrdi, Joseph C. Brdin & Qingfei Xi 1 Rdiofrequeny swithes re ritil omponents in wireless ommunition systems nd onsumer eletronis. Emerging devies inlude swithes sed on miroeletromehnil systems nd phse-hnge mterils. However, these devies suffer from disdvntges suh s lrge physil dimensions nd high tution voltges. Here we propose nd demonstrte nnosle rdiofrequeny swith sed on memristive devie. The devie n e progrmmed with voltge s low s. V nd hs n ON/OFF ondutne rtio up to 1 1 with long stte retention. We mesure the rdiofrequeny performne of the swith up to 11 GHz nd demonstrte low insertion loss (. db t GHz), high isoltion ( db t GHz), n verge utoff frequeny of THz nd ompetitive linerity nd power-hndling pility. Our results suggest tht, in ddition to their pplition in memory nd omputing, memristive devies re lso leding ontender for rdiofrequeny swith pplitions. 1 Nnodevies nd Integrted Systems Lortory, Deprtment of Eletril nd Computer Engineering, University of Msshusetts, Amherst, Msshusetts 1, USA. Rdio Frequeny Nnoeletronis Group, Deprtment of Eletril nd Computer Engineering, University of Msshusetts, Amherst, Msshusetts 1, USA. Correspondene nd requests for mterils should e ddressed to Q.X. (emil: qxi@es.umss.edu). NATURE COMMUNICATIONS :719 DOI: 1.1/nomms & 1 Mmilln Pulishers Limited. All rights reserved.

3 ARTICLE NATURE COMMUNICATIONS DOI: 1.1/nomms19 High-performne swithes re ritil omponents for the rdiofrequeny (RF) iruits tht re widely used in wireless ommunitions nd onsumer eletronis 1. Intense reserh in emerging swith tehnologies hs foused on hieving levels of performne fr eyond tht ville using CMOS (omplementry metl oxide semiondutors) tehnology. Miroeletromehnil system-sed swithes use mehnil movement, usully tivted y voltge/urrent, to ontrol n ohmi or pitive ontt,. Although superior to gllium rsenide nd silion-sed swithes in terms of energy onsumption nd trnsmission properties, miroeletromehnil system swithes suffer from issues suh s speed, dieletri hrging nd ontt interfe degrdtion,. Other devies rely on rerystlliztion nd morphoriztion of phse-hnge mteril (for exmple, germnium telluride) or the metl insultor phse trnsition in strongly orrelted mterils (suh s vndium oxide, VO ) to hnge the resistne stte 9. However, germnium telluride-sed swithes re onstrined y lrge swithing energy nd limited resistne modultion rtio.vo hs n insultor-to-metl trnsition temperture of 7 C (refs 1,11) tht limits the pplition of this devie s RF swith in wider temperture rnge. Even worse is tht the insultor phse trnsition in VO is voltile, whih mens the devie needs to e kept t ove 7 C to mintin low-resistne stte. Furthermore, most of the forementioned emerging RF swithes re of too lrge physil size to permit lrge-sle integrtion with nnometre CMOS RF iruits. Memristive devies re two-terminl resistne swithes whose internl sttes re determined y the history of pplied voltge nd/or urrent 1,1. Swithing is typilly relted to the formtion/rupture of one or more ondutive filments etween two eletrodes through either eletrohemil retions or the migrtion of moile ions tht modulte the interfil properties 1 1. These devies hve demonstrted numer of ttrtive fetures, suh s nonvoltility, low swithing energy (BpJ; ref. 17), fst swithing speed (ons; ref. 1), high endurne (1 1 yles) 19, exellent slility nd CMOS omptiility. As suh, memristive devies re promising ndidtes for universl memory,, reonfigurle its, nonvoltile logi nd unonventionl omputing 7. Here we report nnosle RF swith sed on nonvoltile memristive devie tht onsists of pir of eletrohemilly symmetri metl eletrodes seprted y nnometre-sle ir gp. Different from the forementioned pplitions, RF iruits require swith hving low ON-stte resistne (R ON ) nd low OFF-stte pitne (C OFF ) to hieve high utoff frequeny (f ¼ 1/pR ON C OFF ) while mintining suffiient linerity to e used in prtil wide-nd systems. In the design of our memristive RF swithes, we relized tht the R ON C OFF produt is proportionl to the produt of the resistivity (r) of the ondutive filment nd the effetive dieletri onstnt (e eff ) of the mterils etween the eletrodes (r e eff ). Consequently, we designed devie on thermlly grown silion oxide with two metl eletrodes tht re seprted y n ir gp. The tive metl we used is silver (Ag), whih hs the lowest ulk resistivity (r ¼ O m) mong ll metls, nd the ir gp on silion oxide leds to low effetive dieletri onstnt (e eff E.) for the ir sustrte interfe in the tive devie region. The ility for the swith to funtion within n ir gp, rther thn gp filled with the Ag-doped GeSe film on whih previous nnoioni swithes hve relied, is enled y the nnosle feture size of the demonstrted devie. Our memristive RF swith n e progrmmed with voltge s low s. V nd hs n ON/OFF ondutne rtio up to 1 1. We lso demonstrte low insertion loss (. db t GHz), high isoltion ( db t GHz), typil utoff frequeny of THz nd ompetitive linerity nd power-hndling pility. Results Devie struture nd progrmming. Figure 1 shows the imge nd geometry of typil memristive RF swith. It ws frited on n intrinsi silion wfer (resistivity1, O m) with -nm-thik thermlly grown silion dioxide using photolithogrphy, eletron em lithogrphy (EBL) nd tilted metl evportion (see Methods, Supplementry Fig. 1 nd Supplementry Note 1 for detils). We used gold (Au) with thin titnium (Ti) dhesion lyer s one terminl nd Ag s the other. The terminls were seprted y -nm-wide ir gp. Eh terminl ws onneted to muh thiker (1 mm) opper/luminium (Cu/Al) pd to minimize the ontt resistne with the mesurement proes. Additionl ground pds nd metlliztion were frited t the sme time to permit high-frequeny hrteriztion of the devie within well-defined oplnr wveguide (CPW) environment. The devie exhiited nonvoltile ipolr resistne swithing tht rosses zero in the urrent voltge urve, signture of memristors (Supplementry Fig. nd Supplementry Note 1). We used voltge rmp ( to V or to. V without return sweeps) to progrmme the devie to the ON or OFF stte. A urrent ompline (I ) ws set to minimize the possile dmge to the devie without ffeting the nonvoltility (Fig. ). By pplying mximum sweep voltge of V to the Ag terminl reltive to the Au/Ti terminl, 11-nm-wide ontinuous Ag filment formed within the -nm gp (Fig. ). On the other hnd,.-v is ruptured the filment, progrmming the devie in the OFF stte (Fig. ). Both the high nd low-resistne sttes (OFF/ON) fter progrmming were nonvoltile, s onfirmed y proing with lower voltges (±1 mv). In ddition, the ON/OFF ondutne rtio of the devie ws nerly orders of mgnitude higher thn tht of phse-hnge mteril swith 9 inditing extremely low urrent flow in the OFF stte. We further disovered tht the geometry of the ontinuous silver filment ws dependent on the progrming proess (see Supplementry Fig. nd Supplementry Note ). Under otherwise identil onditions, higher urrent led to filment with lrger dimeter nd hene lower resistne; however, this my lso inrese the energy required for progrmming. The filment formtion initites from the silver side, onsistent with the eletrohemil retion mehnism. However, previously reported devies with similr struture ut lrger gp size hd onsiderly higher resistne euse, rther thn ontinuous metl filment, isolted metl islnds were formed etween the eletrodes,1. We used nrrow gp nd hieved ontinuous filment with low resistne using low progrmming voltges. Devie-retention properties. We did not oserve devie filure from OFF to ON stte up to C. To evlute the ON stte retention of the memristive RF swithes, we mesured the filure time of ON-stte devies t different tempertures. The devie under test ws progrmmed to low resistne t room temperture nd then mounted on losed loop therml huk with n ury of ±. C. The resistne of eh devie ws mesured using semiondutor prmeter nlyser one every minutes until the urrent dropped drmtilly. Figure shows the mesured retention time for our devies t, 11, 1, 1 nd C, whih rnged from 1 to B1 s. We found tht the retention time (t) followed n Arrhenius reltion with respet to temperture (T), 1/tpexp( E /kt), where E is the tivtion NATURE COMMUNICATIONS :719 DOI: 1.1/nomms19 & 1 Mmilln Pulishers Limited. All rights reserved.

4 ARTICLE NATURE COMMUNICATIONS DOI: 1.1/nomms19 Fe e G dl ND in G ND es nm gp d 7 nm Ag Ag 1 nm Au Au Ag Ti 7 nm Ag Adhesion lyer nm SiO nm Si Figure 1 The memristive RF swith is plnr devie with two metl eletrodes seprted y nnometre-sle gp. () A SEM imge of the devie with mirosle thru lines nd nnosle ir gp. Sle r, 1 mm. () Top-view SEM imge of the -nm ir gp (totl length mm). Sle r, nm. () Cross-setionl SEM imge of the ir gp etween the two eletrodes. Sle r, 1 nm. (d) Shemti illustrtion of the geometry for the memristive RF devie. The devie is uilt on n intrinsi silion wfer with -nm-thik thermlly grown silion dioxide. nm Current (A) 1 1 Progrmming ON reding OFF reding Voltge (V) Figure The progrmming of the memristive RF swith is implemented with d voltge sweep nd the ON nd OFF sttes re hieved through the formtion nd rupture of silver filment etween the two eletrodes. () Typil urrent voltge urves for the SET nd RESET proesses for the devie. A. V turned the devie to the ON stte, nd. V sweep turned the devie OFF. The ON/OFF ondutne rtio is nerly 11. Note tht the voltges re the pplied vlue through the instrument. The red nd lue dotted lines re the reding urves using 1 nd 1 mv voltges fter stte hnges, onfirming the nonvoltility of the ON nd OFF sttes. () SEM imge of the devie t the ON stte. The metlli filment is mde of silver nd the dimeter is 11 nm. () At the OFF stte, the filment in is ruptured, leving gp etween the two metl eletrodes. Sle rs, 1 nm. energy for the Ag diffusion nd k the Boltzmnn onstnt. By extending the fitted results to room temperture ( C), the expeted retention time of our devie ws eyond. yers (Fig. ). The long retention time is likely due to the very low moility of Ag toms on the surfe nd inside of silion oxide (. 1 1 m s 1) t room temperture. It should e pointed out tht the retention mesurement in this study ws onduted in ir without pssivtion or other hermeti protetion. The filed devies tested t or elow 1 C ould still e SET to the low-resistne stte using voltge sweep s desried in Fig., inditing tht the swithing ws nondestrutive. The retention time ould e further improved y introduing hermeti sel round the devie. The E extrted from Fig. is.77 ev, whih lies etween the vlue reported for Ag diffusion on SiO surfe (.. ev; refs 7) nd tht for Ag diffusion inside SiO (B1. ev; ref. ). The intermedite tivtion energy suggests tht prt of the ondutive Ag filment ws emedded in the SiO sustrte during the diffusion proess. This is onsistent with previous oservtions tht Ag diffusion ours oth on the SiO surfe nd inside of the SiO simultneously. Temperture nd humidity effets on progrmming voltges. The swithing ehviour is dependent on the mient temperture. As shown in Fig., the SET voltge deresed with higher tempertures, while the RESET voltge ws insensitive to the mient NATURE COMMUNICATIONS :719 DOI: 1.1/nomms19 & 1 Mmilln Pulishers Limited. All rights reserved.

5 ARTICLE NATURE COMMUNICATIONS DOI: 1.1/nomms yers t C 1 1 Current (A) C 11 C 1 C 1 C C Time (s) ln (τ) Mesurement Liner fitting E =.77 ev ,/T (1/K) Figure Retention properties of the memristive RF swith. () Retention mesurement of ON sttes t, 11, 1, 1 nd C. () Temperture dependene of the retention filure time (t) follows the Arrhenius reltion. Retention t C extrpolted from the liner fitting of mesurement results ws B. yers (mrked y str). The tivtion energy E is lulted to e.77 ev. Voltge (V) 1 Voltge (V) Temperture ( C) 1 Reltive humidity (%) Figure Temperture nd humidity dependene of the progrmming voltges. The SET voltge (red) dereses with the temperture () nd reltive humidity (), while the RESETvoltge (lue) does not hnge notiely with these two ftors. The temperture dependeny ws studied under onstnt humidity of %. For the study of humidity dependene, the mient reltive humidity (Hr) ws % (len room mient), % (wter vpour) nd 1% (DI wter immersion), respetively, while the temperture ws fixed t C. Boxplot explntion: upper nd lower ox hinges 7 nd perentiles; the upper nd lower whiskers indite 99 nd 1 perentiles, respetively; the horizontl line within ox represents the medin; the smll ox shows the verge vlue. temperture. This implies tht higher temperture fvours the formtion of n Ag filment during the SET proess 9. The RESET proess is ditted y Joule heting nd the mient temperture does not signifintly ffet the frturing of the filment. The temperture dependeny suggests tht lower progrmming voltge is needed when the devie is used for RF iruits tht operte t C or ove. Furthermore, the progrmming voltge is lso ffeted y the environment humidity (H r ): the SET voltge deresed with higher H r while the RESET voltge remined lmost unhnged (Fig. ). The strong orreltion etween the SET voltge nd the humidity ould e explined oth y the ritil role of moisture in the Ag ioniztion t the node nd y the migrtion of Ag ions during the SET proess. At higher humidity levels, more wter moleules re sored on the SiO surfe. A dense hydrogen-ond network is hene formed tht provides neessry ounter hrges for Ag ioniztion nd lowers the tivtion energy for Ag ion migrtion, leding to smller SET voltge. On the other hnd, the RESET proess of our devie origintes from filment frture due to strong Joule heting nd is thus less influened y moisture. It is worthwhile to point out tht the mient humidity lso ffets the devie endurne (see Supplementry Fig. nd Supplementry Note ). RF performne mesurement nd modelling. We mesured the RF performne of our devies up to 11 GHz using vetor network nlyser (VNA). A multiline thru-reflet-line (TRL) lirtion using set of on-wfer stndrds (Supplementry Fig. nd Supplementry Note ) ws used to ple the mesurement referene plne mm wy from the edge of the intrinsi devie 1,. The trnsmission spetr of devies were otined. In -O environment, the verge OFF-stte isoltion nd ON-stte insertion loss t GHz were nd. db, respetively (exmple urves nd sttistil metris pper in Fig. ). At higher frequenies, the OFF-stte mesurement ws limited y wek oupling to undesired modes supported y the intrinsi silion sustrte. This oupling ould e eliminted if the swith were integrted in thin-film grounded CPW struture (Supplementry Fig. nd Supplementry Note ). We nlysed the smll-signl performne of the nnosle memristive swith using simple physis-sed lumped-element equivlent iruit model shown in Fig.. This equivlent iruit model ws extrted for eh devie nd used to ompute the swith utoff frequenies. Sttistis for the R ON, C OFF nd f re provided in Fig. d. Among the mesured devies, the R ON of the intrinsi swith hs men vlue of. O nd vries from.1 to.9 O. Aording to eletromgneti simultions, the extrted rnge of ON-stte resistne orresponds to nnofilments with ross-setions vrying from B 1 1 to 1 1 m. The C OFF of B1. ff is predominntly ssoited with the pitne of the -nm NATURE COMMUNICATIONS :719 DOI: 1.1/nomms19 & 1 Mmilln Pulishers Limited. All rights reserved.

6 NATURE COMMUNICATIONS DOI: 1.1/nomms19 ARTICLE Memristive RF swith ON stte S 1 (db).1... OFF Stte S 1 (db) 1 1 μm. 1 1 Frequeny (GHz) μ =. db σ =.1 db d 1 1 Frequeny (GHz) μ = 9. db σ =.7 db Ourne 1 Ourne Insertion loss (db) Isoltion (db) Figure Trnsmission hrteriztion of the memristive RF swith. () Typil trnsmission spetrum of devie t the ON stte (solid lue line) with fittings from the equivlent iruit model (dshed red line). The insertion loss t GHz for this devie is lower thn. db. () Trnsmittne spetrum of the devie t the OFF stte (solid lue line) with fittings from equivlent iruit model (dshed red line). The isoltion t GHz is B db. The inset shows the devie struture nd the referene plnes (dotted lines) used for de-emedding. For oth ON nd OFF stte mesurements, pdfrme nd feedline prsitis hve een de-emedded to expose the intrinsi swith performne. (,d) The sttistis for the insertion loss nd isoltion t GHz for the devies we mesured. m nd s re the men vlue nd s.d., respetively. Ourne R ON C OFF μ = 1.7 ff σ =. ff C (ff) OFF Ourne d Ourne R ON (Ω) 7 1 μ =. Ω σ = 1.1 Ω μ =. THz σ = 1.9 THz Cutoff frequeny (THz) Figure Devie modelling nd performne sttistis for mesured devies. () Shemti illustrtion of the devie in the ON stte with equivlent iruit model. The devie is modelled s resistor (R ON ) onneted in prllel with pitor (C OFF ) etween the silver nd gold eletrodes. ( d) Sttistis for the extrted ON-stte resistne (R ON )(), OFF-stte pitne (C OFF )() nd utoff frequeny (f )(d). The verge vlues of R ON, C OFF nd f re. O, 1.7 ff nd. THz, respetively. NATURE COMMUNICATIONS :719 DOI: 1.1/nomms19 & 1 Mmilln Pulishers Limited. All rights reserved.

7 ARTICLE NATURE COMMUNICATIONS DOI: 1.1/nomms19 gp, whih depends on the effetive dieletri onstnt of the sustrte ir interfe. This numer is onsistent with oth eletromgneti simultions nd simple hnd lultions (see Disussion nd Supplementry Note ). The verge vlue of f is THz nd n e further enhned if n identil devie were frited t the top of typil CMOS metl stk tht hs Devie in OFF stte muh thiker SiO lyer. Further enhnement of the smll-signl performne ould lso e hieved y ontrolling the filment geometry to redue RON. We lso evluted the liner performne of the swithes using VNA ple of stndrd two-tone distortion mesurements. The third-order intermodultion interept in the ON- nd OFF- Input power = dbm Input power = 1 dbm Input power = dbm Input power = 1 dbm Input power = 17 dbm Input power = 1 dbm Filment frture point Input power = 9 dbm No selftivtion Devie in ON stte Input power = dbm Input power = 1 dbm Input power = dbm Input power = 1 dbm Input power = 17 dbm Input power = 1 dbm Condutive filment Input power = 9 dbm Frture Output power t filure point (dbm) MHz 1 MHz 1 GHz 1 1 Ron (Ω) Figure 7 Power-hndling pility of the memristive RF swith. () SEM imges of devies t the OFF stte fter tested under different RF input powers t GHz. No self-tivtion ws oserved during the mesurement. () Devie t the ON stte strts self-swithing t 17 dbm. The dimeter of the filment ws 9 nm. Sle rs, 1 nm. () Output power t whih the self-swithing ours for on devies versus on resistne for 1 MHz, 1 MHz nd 1 GHz. Inresing the filment dimeter will improve the RF power-hndling pility for devies in the ON stte. NATURE COMMUNICATIONS :719 DOI: 1.1/nomms19 & 1 Mmilln Pulishers Limited. All rights reserved.

8 NATURE COMMUNICATIONS DOI: 1.1/nomms19 ARTICLE sttes ws evluted using mesurements of series nd shunt swithes to pture relisti operting environment orresponding to single-pole doule throw swith. In oth ses, we found tht the third-order intermodultion interept ws eyond the mesurement limit of þ dbm (Supplementry Figs 7 nd nd Supplementry Note 7). Self-swithing evlution. RF-indued resistne swithing is nother potentil onern with memristive swith due to the su-1 V tution voltge of these devies. We evluted the fesiility for self-swithing under RF power y exiting oth ON- nd OFF-stte devies nd pturing snning eletron mirosopy (SEM) photos s we grdully inresed the RF power (Fig. 7,). A frequeny of GHz ws seleted for these mesurements. We oserved no evidene of self-swithing in mesurements of the OFF-stte devie up to the mximum ville genertor power of þ 1 dbm. However, when mesuring the ON-stte devie, we oserved self-swithing t power level ove þ 17 dbm. We lso investigted the dependene of selfswithing on the frequeny of exittion y mesuring vriety of devies exited with RF energy t 1, 1 nd 1, MHz. In ll ses, we found tht OFF stte devies were not suseptile to self-swithing. Moreover, we oserved little orreltion etween ON-stte power-hndling pility nd RF exittion frequeny. Insted, we oserved strong dependene etween the ON-stte resistne nd the power t whih the devie self-tuted (Fig. 7). The inverse reltionship etween power hndling nd ON-stte resistne is onsistent with Joule heting-sed reset mehnism nd indites tht power hndling n e improved y engineering nnofilments with redued ON-stte resistne (see Supplementry Note for further nlysis). Disussion To further understnd the potentil of the memristive devies s RF swithes, we verified the ON- nd OFF-stte prmeters using full-wve eletromgneti simultion rried out in ANSYS High-Frequeny Struturl Simultor (ANSYS In., Cnonsurg, Pennsylvni). A frequeny rnge of 1 GHz ws seleted nd the sustrte ws mde suffiiently smll to void sustrtemoding effets. A wve-port de-emedding ws employed to set the referene plne of the simultion to tht of the experimentl mesurement. The CPW feedline ross-setion nd silver eletrodes were mde identil to the frited strutures nd -nm gp ws seleted for the tive memristor region. For ON-stte simultions, smll retngulr silver filment ws used to short the gp. The ondutivity of the silver ws redued y ftor of three from its ulk vlue to ount for nnosle effets. The thikness nd width of the filment were vried to study the impt of the filment dimension on the ON-stte resistne. The predited OFF-stte trnsmission ppers in Fig.. At GHz, the predited isoltion is 1 db, whih is within 1 db of the mesured vlue ( db) s shown in Fig.. Moreover, the predited isoltion remins etter thn 17 db to GHz. The OFF-stte pitne ws lulted s C OFF ¼ img{1/y 1 }/o. The result is plotted in Fig.. Over rod rnge of frequenies, the predited pitne is 1.17 ff, whih is onsistent with oth hnd lultions nd mesurement. Moreover, the frequeny independene of the extrted pitne vlidtes our use of the simple lumped element equivlent iruit. The simulted trnsmission of the ON-stte devie is shown in Fig. for filments with ross-setions of 11 nm 7 nm nd nm 1 nm. The verge experimentlly otined insertion loss vlue (. db) orresponds to nnofilment of rosssetion 1 1 m, whih is signifintly smller thn expeted sed on SEM imging. This indites tht signifint omponent of the RF resistne my e relted to ontt resistne. The orresponding ON-stte resistne is plotted versus frequeny in Fig. d. The memristive RF swith requires no power to mintin the ON or OFF stte, potentilly leding to power effiieny OFF stte S 1 (db) ON stte S 1 (db) Frequeny (GHz) nm... 1 nm Frequeny (GHz) OFF pitne (ff) d ON resistne (Ω) Frequeny (GHz) Frequeny (GHz) 1 nm 11 7 nm Figure Eletromgneti simultion results using High-Frequeny Struturl Simultor (HFSS). () OFF-stte trnsmission; () OFF-stte pitne; () ON-stte trnsmission; nd (d) ON-stte resistne for two filment ross-setions. NATURE COMMUNICATIONS :719 DOI: 1.1/nomms & 1 Mmilln Pulishers Limited. All rights reserved.

9 ARTICLE NATURE COMMUNICATIONS DOI: 1.1/nomms19 dvntges. The low progrmming voltge enles monolithi integrtion of memristive RF swithes with low-power CMOS iruits to expnd the funtionlity. The devie frition proess for our memristive RF swithes is lso simpler s ompred with other devies. Further sling of the devie, suh s shrinking the gp size, will led to optimized swithing ehviour suh s longer endurne nd lower power onsumption, with no degrdtion to the RF performne, provided the ON-stte resistne is dominted y the filment nd not other effets. It is neessry to engineer the lotion nd geometry of the metlli filments for even lower ON-stte resistne, to enhne the devie endurne, nd to redue the energy required for eh swithing event. Nonetheless, we elieve tht memristive RF swithes will eome one of the leding ontenders in RF iruits for ommunition nd onsumer eletronis. Methods Devie geometry nd frition. The memristive RF swithes were uilt on n intrinsi silion wfer (resistivity1, O m) with -nm-thik thermlly grown oxide. The frition proedure involved three mjor steps tht defined the mirosle ontt pds, the CPW struture nd the nnosle gp. The mirosle fetures were ptterned y photolithogrphy using -nm wvelength ultrviolet rdition, nd the nnogp ws defined using EBL. The pdfrme nd feedline strutures onsisted of 1-nm-thik Ti dhesion lyer nd 1-nm-thik gold lyer, oth deposited in n eletron em evportor. The distne etween the entrl eletrodes ws mm. The ontt pds were mde of 1-mm-thik Cu nd -nm-thik Al tht were deposited y RF mgnetron sputtering. Before friting the nnometre-sle gp, retngulr window of mm y mm ws opened y EBL in the entre re of the eletrodes. The nnogp ws reted y evporting 7-nm-thik Ag with tilted ngle. For the -nm gp, the evportion ngle ws reltive to the wfer surfe. See Supplementry Note 1 for the detiled frition proedure nd shemtis. DC progrmming. The devies were progrmmed to the ON- or OFF-stte with qusi-dc voltge sweeps using Keithley SC semiondutor prmeter nlyser. A urrent ompline ws set to protet the devie, nd to ontrol the size nd morphology of the metlli filment. During the progrmming, the inert metl eletrode ws grounded nd the silver eletrode ws ised. A positive voltge will SET the devie to low resistne y ridging the nnogp, while negtive voltge ruptures the filment nd RESETs the devie to the high-resistne stte. RF mesurements. Smll-signl mesurements were rried out ON-wfer using n Agilent N7A VNA with pir of N frequeny extender modules, permitting mesurements to e rried out from.1 to 11 GHz. To minimize sustrte-moding when mesuring the OFF-stte-sttering prmeters, the swithes were first singulted to size of B1mm 1mm. mm (length width height) nd then mounted using photo-resist on rigid sorer omposed of ron-loded epoxy. For smll-signl mesurements, the RF power ws set to nominl level of dbm. A multiline TRL lirtion ws rried out from 1 to 11 GHz using set of stndrds frited on n identil sustrte s the memristive swithes (further detils re provided in the Supplementry Note ). The multiline TRL lirtion 1, pled the mesurement referene plne mm from the edge of the intrinsi devie. No dditionl de-emedding ws employed. A seond lirtion using the LRM þ lgorithm rried out on Csde 1-7 lirtion sustrte ws employed to mesure the devies, referened t the plne of the ondpds so tht omprison of the ON-stte devie to thru line ould e mde (Supplementry Fig. 9 nd Supplementry Note ). All lirtions were performed using Csde WinCl softwre (Csde Miroteh In., Beverton, Oregon), efore devie mesurement, llowing for dt t the two referene plnes to e quired simultneously. Sttering prmeters were olleted for eh devie in oth the ON- nd OFF-sttes, nd prmeter extrtion ws rried out to determine the ON- nd OFF-stte equivlent iruit models. Two-tone linerity mesurements were rried out t GHz with 1-MHz-tone sping nd swept power level rnging from to þ 7 dbm. Power hndling ws evluted in the ON- nd OFF-sttes y driving the memristor with lortory CW soure (Agilent PSG7D) nd mesuring the output power using spetrum nlyser (Agilent N91A). The power ws swept from to þ 1 dbm, with steps of 1 dbm for three different frequenies inluding 1 MHz, 1 MHz nd 1 GHz. All le losses were determined nd de-emedded. The detiled evolution of one ONstte nd one OFF-stte devie ws studied y inrementlly pturing SEM imges s the devies were grdully exposed to higher RF power levels. For this experiment the RF power swept from to 1 dbm with steps of dbm nd the frequeny ws set to GHz. SEM photos were otined t eh step. Referenes 1. Brown, E. R. RF-MEMS swithes for reonfigurle integrted iruits. IEEE Trns. Mirow. Theor. Tehn., 1 1 (199).. Griffith, D. J. Introdution to Eletrodynmis (Prentie Hll, 1999).. Yo, J. J. RF MEMS from devie perspetive. J. Miromeh. Miroeng. 1, R9 R ().. Reeiz, G. M. RF MEMS: Theory, Design nd Tehnology (John Wiley & Sons, ).. Reeiz, G. M. et l. Tuning in to RF MEMS. IEEE Mirow. Mg. 1, 7 (9).. El-Hinnwy, N. et l. In Compound Semiondutor Integrted Ciruit Symposium (CSICS) 1 IEEE, 1 (Monterey, CA, USA, 1). 7. Wng, M., Shim, Y. & Ris-Zdeh, M. A low-loss diretly heted two-port RF phse hnge swith. IEEE Eletron Dev. Lett., 91 9 (1).. Moon, J., Seo, H. & Le, D. In Mirowve Symposium Digest 1 IEEE MTT-S Int., 1 (Tmp, FL, USA, 1). 9. Hillmn, C. et l. In Mirowve Symposium Digest 1 IEEE MTT-S Int., 1 (Tmp, FL, USA, 1). 1. Morin, F. J. Oxides whih show metl-to-insultor trnsition t the Neel temperture. Phys. Rev. Lett., (199). 11. Mott, N. F. & Friedmn, L. Metl-insultor trnsition in VO, TiO nd Ti-xVxO. Philos. Mg., 9 (197). 1. Chu, L Memristor-the missing iruit element. IEEE Trns. Cir. Theor. 1, 7 19 (1971). 1. Strukov, D. B., Snider, G., Stewrt, D. & Willims, R. S. The missing memristor found. Nture, (). 1. 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10 NATURE COMMUNICATIONS DOI: 1.1/nomms19 ARTICLE 7. Kim, H. C., Alford, T. L. & Alle, D. R. Thikness dependene on the therml stility of silver thin films. Appl. Phys. Lett. 1, 7 9 ().. Sun, H. et l. Diret oservtion of onversion etween threshold swithing nd memory swithing indued y ondutive filment morphology. Adv. Funt. Mter., 79 (1). 9. Wser, R., Dittmnn, R., Stikov, G. & Szot, K. Redox-sed resistive swithing memories nnoioni mehnisms, prospets, nd hllenges. Adv. Mter. 1, (9).. Tppertzhofen, S. et l. Generi relevne of ounter hrges for tion-sed nnosle resistive swithing memories. ACS Nno 7, 9 (1). 1. Mrks, R. B. A multiline method of network nlyzer lirtion. IEEE Trns.Mirow. Theor. Teh. 9, 1 11 (1991).. Willims, D. F., Wng, C. M. & Arz, U. Mirowve Symposium Digest, IEEE MTT-S Int (Phildelphi, PA, USA, ).. Bid, A., Ahyut, B. & Ryhudhuri, A. K. Temperture dependene of the resistne of metlli nnowires of dimeter Z 1nm: ppliility of Bloh- Grüneisen theorem. Phys. Rev. B 7, ().. Tere, K., Hsegw, T., Nkym, T. & Aono, M. Quntized ondutne tomi swith. Nture, 7 ().. Zhirnov, V. V., Mede, R., Cvin, R. K. & Sndhu, G. Sling limits of resistive memories. Nnotehnology, 7 (11). Aknowledgements This work is supported in prt y the Defense Advned Reserh Projets Ageny (DARPA; N ; N ), the Ntionl Siene Foundtion (NSF; ECCS-17) nd the Air Fore Offie of Sientifi Reserh (AFOSR; FA9-1-1-). Prt of the devie frition ws onduted in the len room of Center for Hierrhil Mnufturing (CHM), n NSF Nnosle Siene nd Engineering Center (NSEC) loted t the University of Msshusetts Amherst. We thnk Peng Lin for growing the therml oxide on the intrinsi silion wfers nd prepring ross-setionl SEM imging smples using foused ion em (FIB) mirosope; Roert Jkson, Willim Chppell nd Roy Olsson for disussion; nd J. Joshu Yng nd Sigfrid Yngvesson for ritil omments on the mnusript. Author ontriutions Q.X. nd J.C.B. oneived the ide. Q.X. nd S.P. designed nd frited the devie, nd did the DC mesurements nd progrmming. J.C.B. nd M.G.-S. mesured nd modelled the RF performne. Q.X. nd J.C.B. wrote the min text, ll uthors wrote the Supplementry Informtion nd ommented on the entire mnusript. Additionl informtion Supplementry Informtion ompnies this pper t ntureommunitions Competing finnil interests: The uthors delre no ompeting finnil interests. Reprints nd permission informtion is ville online t reprintsndpermissions/ How to ite this rtile: Pi, S. et l. Nnosle memristive rdiofrequeny swithes. Nt. Commun. :719 doi: 1.1/nomms19 (1). NATURE COMMUNICATIONS :719 DOI: 1.1/nomms & 1 Mmilln Pulishers Limited. All rights reserved.