Fabrication and characterization of ultra-thin magnetic films for biomedical applications

1182 IEEE TRANSACTIONS ON NUCLEAR SCIENCE, VOL. 60, NO. 2, APRIL 2013

Fabrication and Characterization of Ultra-ThinPIN Silicon Detectors for Counting the

Passage of MeV IonsNaseem Abdel, Jan Pallon, Mariusz Graczyk, Ivan Maximov, and Lars Wallman

Abstract—This paper describes the fabrication and initial char-acterization of an ultra-thin silicon PIN detector using a new tech-nique in silicon nanotechnology. In collaboration with the NuclearPhysics Division and the Lund Nano Lab at Lund University, wehave developed and manufactured ultra thin -detectors forspectroscopic applications. The fabrication process has been car-ried out using a double-polished silicon substrate n-type wafer andlocally thinning by means of a 10:1 solution of 25% tetramethylammonium hydroxide (TMAH) with Isopropyl alcohol. More than100 detectors of different thicknesses, down to 5 with activeareas ranging from 0.71 to 0.172 , have been fabricated. Themain design considerations of our thin detectors were a very lowleakage current below 12 nA and a low full depletion voltage ata reverse bias less than 1.5 V. Finally, most of our thin detectorsoffer an energy resolution (FWHM) as low as 31 keV for 5.487MeValpha particles from a source.

Index Terms—Energy resolution, leakage current, silicon nano-technology, TMAH etching, ultra-thin PIN detector.

I. INTRODUCTION

T HE last few years have seen a remarkable change in semi-conductor radiation detectors and radiation detection sys-

tems. Some studies have focused on silicon nano-technologydevelopments to fabricate detectors with thicknesses less than 5

[1], [2] called ultra-thin PIN silicon detectors.The thin silicon detector is used as a -detector

in many applications within a telescope configuration forthe tracking and identification of fragments of nuclear reactionsin nuclear experiments. It has been used to detect the energy lossof high energy particles so as to identify the charge and massof the particles [2], [3]. They are used in applications for the

Manuscript received June 01, 2012; revised August 29, 2012; acceptedNovember 20, 2012. Date of publication January 14, 2013; date of currentversion April 10, 2013. This work was supported in part by the SwedishResearch Council Grant number 2008-5261.N. Abdel is with the Laboratory of Lund Ion Beam Analytical Facility,

Physics Department, Division of Nuclear Physics, Lund Institute of Technology,Lund University, 221 00 Lund, Sweden (e-mail: [email protected]).J. Pallon is at the Laboratory of Lund Ion Beam Analytical Facility, Lund

Institute of Technology, Lund University, 221 00 Lund, Sweden (e-mail: [email protected]).M. Graczyk and I. Maximov are with Lund Nano Lab, Division of Solid

State Physics, LTH, Lund University, 221 00 Lund, Sweden (e-mail: [email protected]; [email protected]).L. Wallman is with Nano Biotechnology and Lab-on-a-chip, Department of

Electrical Measurement, LTH, Lund University, 221 00 Lund, Sweden (e-mail:[email protected]).Color versions of one or more of the figures in this paper are available online

at http://ieeexplore.ieee.org.Digital Object Identifier 10.1109/TNS.2012.2230644

nuclear industry when short range particles are to be detectedunder high gamma ray backgrounds, due to higher radiation se-lectivity when compared to standard thick silicon E-detectorswith thicknesses ranging from 300 to 500 . Such telescopesare widely used in nuclear physics and materials science [4], [5].Most research interests have been focused on new fabrica-

tion techniques of ultra-thin silicon detectors because they arevery difficult to handle and process. However, many scientistshave been seeking to develop thinner detectors to be usedas transmission detectors in systems where the biological effectsof single ion irradiation on living cells are studied. It was re-cently proposed to introduce the detector for pre-cell detec-tion to improve the control of beam dose to suppress extra pas-sages ions and scattered particles [6], [7]. At the Lund Ion BeamAnalytical Facility (LIBAF)/Lund University/Sweden, the thinpre-cell silicon detector has been used to detect the passage of2.5 MeV protons, introducing a minimum of ion straggling andscattering.The ultra-thin PIN silicon detector has extra strict require-

ments such as low leakage current, low full depletion voltage,active area thickness and mechanical reliability. Many scientistshave been interested in overcoming these problems and haveintroduced thin detectors with good energy resolution [6], [7].Thungström et al., [2] have pioneered the fabrication of thin sil-icon detectors having thicknesses down to 5 , which displaya leakage current close to 2n A at a reverse bias voltage ofand a capacitance close to 300 pF. However, in this application,more than 100 ultra-thin PIN silicon detectors have been fab-ricated with different physical parameters (thickness and activearea) at different concentrations of substrate doping, which areintroduced in this paper. We report the systematic testing, in-cluding electrical tests of I-V, C-V characteristics and energyresolution (FHWM) for alpha particles, which is carried out inorder to evaluate the fabrication process and the device. Thewet etching technique using TMAH, is low cost, quickly etchesa smooth surface and has a good selectivity for most materials,compared to the plasma etching technique which is character-ized by high cost, low fabrication throughput, poor selectivityfor many materials [8].

II. ULTRA-THIN PIN DETECTOR FABRICATION

The ultra-thin PIN silicon detectors have been fabricated inthe Lund Nano Lab, Division of Solid State Physics in collab-oration with the Nuclear Physics and the Electrical Measure-ments Divisions at Lund Institute of Technology, Lund Univer-sity, Sweden. The ultra-thin PIN silicon detector is illustrated

0018-9499/$31.00 © 2013 IEEE

ABDEL et al.: FABRICATION AND CHARACTERIZATION OF ULTRA-THIN PIN 1183

Fig. 1. Cross-sectional view of ultra-thin PIN silicon detector.

in Fig. 1 which consists of two main parts, a supporting sub-strate with a thickness of about and a mainjunction area which involves an active area where the substratethickness changes abruptly.The PIN silicon detector fabrication process starts from

a silicon substrate wafer (n-type). It is characterized by ahigh resistivity (4000 ), a thickness ofwith a double-polished oriented 2 inch wafer anda background dopant concentration by phosphorus of about4 . The fabrication process starts with astandard cleaning process of the wafers, using a solution of

having a volume ratio of 2.5:1 for 10 min fol-lowed by a rinsing for 5 min in de-ionized water (Fig. 2(a)).A 2 thick layer is grown on both sides of the waferby thermal wet oxidation (Fig. 2(b)). And then a 10:1 BufferedHydrofluoric Acid (BHF) solution is utilized to patternlayer on the front side (the side with is defined as the frontside) where the backside of wafer is protected by depositingabout 1.3 Photoresist (S-1818) as a mask (Fig. 2(c)). Inorder to form n-type at the front side of the wafer, a diffusiondoping process was performed using a solid phosphorous-oxide

crystalline diffusion source at a temperature of900 for 30 minutes in nitrogen ambient (Fig. 2(d)). In orderto prevent auto doping, a 800 nm layer was grown on bothsides of the wafer, which also was acting as the hard mask forbackside patterning (Fig. 2(e)). At the backside of the wafer,detector windows were defined in the oxide with an area ofquadratic shape, using a UV-lithography with mask definition(Fig. 2(f)). Then the BHF solution was used to etch the oxideunderneath to dehydrate the detector windows (Fig. 2(g)).These windows were etched in a mixed solution 10:1 of 25%tetra-methyl ammonium hydroxide (TMAH)with Isopropyl Alcohol (IPA) at 80 for approximately 10hr or until the desired thickness of the wafersubstrate [8] was reached (Fig. 2(h)). A 10% by volume ofIPA was added to the solution to get a smooth surface and toreduce the reaction rate, this is due to low dielectric constantof IPA [9], [10]. The backside detector window was dopedwith boron to form a p-type layer by thermal diffusion usinga solid boron-oxide source at 950 for different dopingtimes (45, 60 and 90 minutes) in nitrogen ambient (Fig. 2(i)).Immediately after doping the backside detector window, a700 nm aluminum layer was deposited on both sides of thewafer, using the evaporator machine (model UNIVEX 300).

Fig. 2. Flowchart of ultra-thin PIN detector fabrication process.

The thickness of the aluminum layer was chosen to reduce apotential channeling effect, as presented by Lugujjo and Mayer[11]. The silicon dioxide in the front side of the wafer wasthen removed (Fig. 2(j) and (k)). Most metal-semiconductorcontacts are annealed after the initial deposition of the metalin an effort to further improve the contact resistivity. A RapidThermal Annealing furnace (Model RTP 1200) was used toanneal the wafers prototype at 400 for 4 min in ambient gas

.The last step before packaging was the precision cutting of

the sensor out of the wafer with a diamond saw. A sketch of thefinal detector structure can be seen in Fig. 1 and the structureparameters of device design are summarized in Table I.


TABLE ISTRUCTURE PARAMETERS OF OUR FABRICATION

Fig. 3. (a) Cross section of the thin detector after package, (b) Photograph viewseen from the back side of detector.

III. PACKAGING

The purpose of the package is to link the non active part (Sup-porting frame) of the detector piece to its outside world (calledhousing frame). The package process is to facilitate the han-dling and connection [12], [13]. A housing frame, as illustratedin Fig. 3, was designed for this detector. The housing body wasfabricated using a 10 mm thick piece of plastic (Plexiglass) withdimensions of 20 20 mm. A plastic cap was also glued on thedetector housing to protect the detector’s surface. Thereafter,gold plated pins were placed at the surface of the housing to beused as detector electrodes. In addition, electrical wires (con-tact pins) were soldered to the electrodes. Finally, microwireswere attached using an ultrasonic bonding machine (model K& S 4523) on both the front side and backside of the detector’spiece.

IV. PHYSICAL PARAMETERS CHARACTERIZATION

Several physical parameters are varied in the fabricationprocess to find the optimum performance of the thin detectorwhich will used as the primary triggers in single ion irradiationexperiments. The main parameters are: i) the detector activearea, ii) the active area thickness, iii) the boron diffusion timewhich is related to the p-type area and finally, iv) annealingtreatment. The boron diffusion takes place at high temperature(near to 950 ) and with a long process time that is necessaryto obtain high concentrations and large junction depths [8].

Fig. 4. Photograph of 5.6 thick detector having an active area of0.72 0.72 and seen from the back side which appears also the edge andS. frame (supporting frame) of detector.

Fig. 5. The set up of equipment of thickness measurement configuration.

Thus, depending on these physical parameters, the fabricateddetectors are divided into three groups (Group 1, Group 2and Group 3) depending on the boron diffusion time: 45, 60and 90 minutes, respectively. In addition, these groups areclassified into a reference and an annealing class depending onthe presence or absence of the annealing treatment at 400 ,before packaging process.In order to measure the thickness and the active area for more

than 100 fabricated detectors, we utilize the one technique asdescribed below

A. Active Area Dimensions of Thin Detector

A Microscope (model Axio Imager A1m Zeiss) at the LundNano Lab, was utilized to measure the active area of the fab-ricated detectors. This area corresponded to the mask’s dimen-sions during the lithography process. For instance, Fig. 4 showsthe 0.72 0.72 mm active area of thick de-tector, and it illustrates also the supporting a frame and the edgeof detector which is induced during the etching process of the

oriented wafer.

B. Thickness Measurements

Thickness measurements of more than 100 thin detectorswere carried out using an alpha particle source and athick (stop) silicon detector [3] in the configuration shown inFig. 5. The 300 thick Hamamatsu silicon detector, whichhas an active area 4 4 and reverse bias of 30 V, wasconnected to standard electronics to acquire spectral data.Furthermore, the thick detector was placed inside a measure-ment chamber under the vacuum of 5 . An energycalibration was performed using the alpha particle energy of5.487 MeV.Our thin detectors were put in front of the thick detector in-

side the measurement chamber as illustrated in Fig. 5. Under the


Fig. 6. Spectrum for E-detector with presence and absence ofthick detector.

irradiation process, the transmitted energy through the de-tector was measured by the E-detector. It was compared with astandard spectrum that was produced without the -detectorpresent. Therefore, the difference between the alpha particles’senergy and the energy measured with -detector by the E-de-tector is equal to the energy loss in the detector, as shown inFig. 6. It shows a spectrum from the E detector with and withouta thick detector, which has a energy lossaround 0.77 MeV.In order to estimate the detectors’ thickness, the

energy loss was simulated using the SRIM-2011 [14] foralpha particles having an energy of 5.487 MeV. In this thesimulation, a composition of our thin silicon detector wasassumed to be

. The following simulation equation(see Fig. 7) was found to relate the detector thickness,and the energy loss (MeV) through the detector:

(1)

Thus, by measuring the energy loss through each of the thindetectors, their thicknesses were calculated using (1).

V. ELECTRICAL CHARACTERIZATION

In order to evaluate the performance of our ultra-thin PIN de-tectors, basic electrical tests were performed including currentversus voltage (I-V), a capacitance versus voltage (C-V) mea-surements and also testing of noise performance [12], [13].

A. (I-V) Measurements

The leakage current increases linearly with detector thick-ness and then as a function of the applied bias voltage, but toomuch current will deteriorate or even totally destroy the realsignal. The I-V measurements of our fabricated detectors wereperformed using a probe station (Model Cascade 11000B) atthe Lund Nano Lab and the leakage currents of detectors wererecorded when biased by a reverse voltage from 0 V to .

Fig. 7. Simulation of energy loss in detector componentsfor an alpha particles energy

of 5.486 MeV.

Fig. 8. Leakage current tests for thin detectors: No. 2Group 3 ,No. 4 Group 2 at annealed detectors and No. 6 Group 1

from references detectors.

Fig. 8 illustrates the I-V characteristic of athin detector from the reference class, while and

thin detectors have been selected from the an-nealing class. The figure shows that the leakage current, denoted, increases linearly with applied bias voltage until the detector

becomes fully depleted, where the current becomes saturatedand called the reverse saturation current , as depicted in (2)and (3) [15].

(2)

(3)

Where is elementary charge, is the applied bias voltage,is Boltzmann constant, is the absolute temperature, is thecross-sectional area, are the diffusion coefficients of holesand electrons, respectively, are the donor and acceptorconcentrations at the n side and p side, respectively. While isthe intrinsic carrier concentration in the semiconductor material


Fig. 9. Calculated full depletion voltage as function of the PIN detector’sthickness.

and and are the carrier life times of impurities of dopantatoms (holes and electrons), respectively.Therefore, all the tested detectors with a reverse bias voltage

below have reverse saturation currents not exceeding9 and 12 nA for the annealed and reference detectors, respec-tively. This decline in the leakage current after the thermal an-nealing process is due to minimization the role of recombinationand trapping centers [8]. This behavior of a leakage current isalmost similar for all our fabricated detectors at both classes asillustrated above.

B. (C-V) Measurement

The relation between the bulk capacitance and full depletionvoltage of the PIN detector can be calculated according to theapplied bias voltage, and is given by (4) and (5) [13]:

(4)

(5)

Here is the active area of the junction, is the relative per-mittivity of silicon, is the electronmobility, is the resistivityof the bulk region and is the full depletion thickness of the PINdetector. However, according to the equations above, the capac-itance will almost keep stable when the detector becomes fullydepleted. Therefore, the full depletion voltage as function of thedetector’s thickness was calculated and shown in Fig. 9.The C-Vmeasurements for the thin detectors were performed

using a recision Impedence Analyser (Agilent). The test resultsof a number of the detectors which have been selected from bothclasses, are illustrated in Figs. 10 and 11. The figures show thatthe capacitance for some thin detectors have a slight drop atfirst and then almost keep stable when the reverse bias voltageincreases, indicating that the detector became fully depleted.Thus, at the full depletion region, the generation volume of elec-tron and hole pairs for the detector was increased. However, ourresults showed that the thin detectors became fully depleted ata bias voltage less than with capacitances ranging from

Fig. 10. C-V characteristic of the ultra-thin PIN detectors: (No.18 (G1),, ), (No.5 (G2), ,

), (No.1 (G3), ,) and (No. 8 (G3), , )

for reference class.

Fig. 11. C-V characteristic of the ultra-thin PIN detectors: No. 10 (G2),, ), (No. 1 (G3),, ), (No. 2 (G3),, ) and (No. 4 (G3),

, ) for annealing class.

36.9 pF to 28.01 pF and 25 pF to 17.23 pF for the reference andannealed detectors, respectively. Therefore, the measured valueof a full depletion voltage of agree with the calculatedvalue at detector’s thickness down to 30 , as demonstratedin Fig. 9. Also, the measured results of the capacitance values atfull depletion voltage of the annealed detectors were observedto be less than other of the reference detectors. This a varia-tion between the both classes, is due to the parasitic capacitancearound the metal oxide semiconductor contact, which is close tothe supporting frame, causing a stress accumulation around themain junction. Subsequently, the accumulation of chargecarriers at the junction volume leads to a slower depletion. Thiseffect is appears to be more expressed for the reference detec-tors [2].On the other hand, we obtained other detectors which have

a complete depletion at zero bias voltage. It is illustrated in thefigures below for detectors no. 5 and no. 10 with almost similarthickness at a 45 minutes boron diffusion time. The operating


Fig. 12. Schematic diagram of the experiment equipment’s connection.

TABLE IITHE ENERGY RESPONSE OF THIN DETECTORS AT REFERENCE CLASS

zero voltage is probably due to a higher diffusion coefficientat higher boron concentrations [8], indicating the effect of theboron diffusion time.

VI. DETECTION CHARACTERIZATIONS

In next step, the ultra-thin PIN detectors were connected toa particle detecting system to observe the energy resolution(FWHM), noise level [7], [15] and response to irradiation of5.487 MeV alpha particles from a source during a 180minutes, see Fig. 12. The thin PIN detector was connected to alow noise charge preamplifier (type A) whose out put was fedinto a shaping amplifier with a shaping time of 0.5 . Thespectral response was digitized and recorded by a PC-basedmulti-channel analyzer and data acquisition system (MaestroModel A65-B32). In order to obtain an energy calibratedsystem, a thick PIN silicon detector with activearea of 1.5 1.5 and being reverse biased at 10 V, wasselected. Because of the detector thickness the alpha particlesdeposit all energy within the detector. This detector was fab-ricated with the same properties as the thin detectors, and thecalibration found here was used for all thin detectors tested. Inorder to figure out how much the PIN detector contributes tothe energy resolution, we first tested electronically cut off thecontribution of electronic noise which comes from an electronicdevices and the detector, to the energy resolution of the system.Our measured results show that the noise peak of all fabricateddetectors was located at around 74.5 keV.The deposited energy of alpha particles through the thin de-

tector was used to investigate the spectral response of more than100 thin PIN detectors. Our experimental results are summa-rized in Tables II and III for a number of the thinnest fabricateddetectors selected from the reference and annealing classes.The Tables II and III shows the FWHM values and peak posi-

tions (deposited energy in the detector, keV) of some thin detec-tors. The measured results of the FWHM values of the annealed

TABLE IIITHE ENERGY RESPONSE OF THIN DETECTORS AT ANNEALING CLASS

Fig. 13. Spectral response of source of a andthin PIN silicon detectors from group 3 annealed and reference classes

respectively, compared with the pulse height spectrum of the 300 thick PINstandard detector.

detectors were observed to be better, in a range 31.1–65 keV,compared to the reference detectors, being in a range 56–159keV. This large variation in the FWHM is mainly due to the re-duction of roughness of the aluminum surface by the annealingprocess which is usually used to obtain a clean, smooth and wellordered silicon surface [16]. This decreases the particle scat-tering when passing through it, and leads to a decrease in thespread of the FWHM values.The tables also show that the energy responses for the an-

nealed detectors were better compared with the reference de-tectors. It is probably due to an increase in the charge collectionefficiency after the thermal annealing process that reduce trap-ping-detrapping effects. In addition, we could make a conclu-sion that the detectors from group 3 of both classes were moreefficient to detect the alpha particles.Fig. 13 shows the nuclear pulse height spectrum for the

and thin detectors overlayed to be com-pared with the pulse height spectrum of a thick standard de-tector. Our results show that the FWHM values are 37 keV and98 keV for the and thin detectors,respectively, compared to 29 keV for a 300 thick silicondetector.These results are in accordance with [6] that observed an en-

ergy resolution of 110 keV for a silicon detector of 10 thick-ness and 4 active area. The difference in FWHM valuesbetween thin and thick detectors is mainly due to the partialamount of energy that is deposited in the thin detector compared


to the thick detector. Thus, this leads to an increase in the statis-tical straggling of particles and consequently a broader spectrumpeak shape for the thin detectors.

VII. CONCLUSION

Ultra-thin silicon PIN detectors down to a thickness of 5with active areas ranging between 0.71 to 0.172 , havebeen fabricated and characterized successfully using our tech-nology process. Wet etching by TMAH solution with Isopropylalcohol 10:1 thinning silicon method is a convenient techniqueto fabricate ultra-thin detectors with a smooth surface. It hasalso good selectivity for most materials with very low contam-ination and is nontoxic. According to our measurements, mostof the ultra-thin detectors have a leakage current below 12 nAand reach full depletion at a bias less than . The capac-itances are ranging from 28.85 to 36.9 pF and 17.25 to 27.89pF for the reference and annealed classes, respectively. The res-olution FWHM values for thin annealed detectors are smallerthan for detectors of the reference class. Furthermore, the thindetectors from group 3 (having longer boron diffusion time) ofboth classes showed excellent performance and had high effi-ciency, compared with other groups and according to their en-ergy response. Moreover, the fabrication process developmentis in progress in order to reduce the leakage current of the de-vices and increase the energy resolution.

ACKNOWLEDGMENT

N. Abdel thanks the staff in the Lund Ion Beam AnalyticalFacility laboratory and Lund Nano Lab at the Lund Universityfor their help in the fabrication of the devices and also thankV. Avdeichikov and P. Golubev from the Nuclear Physics atLund University for valuable discussions and help in packagingand characterization the detectors.

REFERENCES[1] V. V. Avdeichikov, “Ultra-thin strip silicon detectors,” Nucl. Instrum.

Meth. Phys. Res., vol. A313, pp. 561–562, 1992.[2] G. Thungström, L. Westerberg, R. Spohr, and C. S. Petersson, “Fabri-

cation and characterization of thin detectors for spectroscopic ap-plication,” Nucl. Instrum. Meth. Phys. Res., A, vol. 546, pp. 312–318,2005.

[3] L. Evensen et al., “Thin detectors for the CHICSi telescope,”IEEE Trans. Nucl. Sci., vol. 44, pp. 629–634, 1997.

[4] E. J. C. Nilsson, J. Pallon, G. Thungström, N. A. Marrero, M. Elfman,P. Kristiansson, C. Nilsson, and M. Wegdén, “Characterisation of apre-cell hit detector to be used in single cell irradiation experimentsat the Lund Nuclear Microprobe,” Nucl. Instrum. Meth. Phys. Res., B,vol. 266, pp. 4808–4815, 2008.

[5] E. J. C. Nilsson, J. Pallon, G. Thungström, N. A. Marrero, M. Elfman,P. Kristiansson, C. Nilsson, and M. Wegdén, “Evaluation of a pre-cellhit detector for the future single ion hit facility in Lund Nuclear,” In-strum. Meth. Phys. Res. B, vol. 249, pp. 924–927, 2006.

[6] F. Foulon, L. Rousseau, L. Babadjian, S. Spirkovitch, A. Brambilla,and P. Bergonzo, “A new technique for the fabrication of thin silicon ra-diation detectors,” IEEE Trans. Nucl. Sci., vol. 46, no. 3, pp. 218–220,Jun. 1999.

[7] Y. Li, S. Ma, Y. Jin, M. Yu, L. Zhang, and J. Wang, “Fabricationand characterization of ultra-thin PIN detector,” in Proc. 5th IEEE Int.Conf. Nano/Micro Engineered and Molecular Systems, Jan. 2010, vol.20–23, pp. 505–509.

[8] S. M. Sze, Semiconductor Devices, Physics and Technology, 2nd ed.New York: Wiley, 2002.

[9] K. B. Sundaram, A. Vijayakumar, and G. Subramanian, “Smoothetching of silicon using TMAH and isopropyl alcohol for MEMSapplications,” Microelectron. Eng., vol. 77, pp. 230–241, 2005.

[10] A. M. M. Acero, M. H. Bao, J. Bausells, and J. Esteve, “TMAH/IPAanisotropic etching characteristics,” Sens. Actuators, A, pp. 37–38,1993.

[11] E. Lugujjo and J. W. Mayer, “Energy dependence of andchanneling in Si overlaid with Au films,” Phys. Rev. B7, pp.

1782–1791, 1973.[12] K. Maschida, “Interconnect technology in the 1990s,” in Surface

Mount Technology. Piscataway, NJ: IEEE Press, 1993, pp. 3–12.[13] F. Hartmann, Evolution of Silicon Sensor Technology in Particle

Physics. Berlin Heidelberg: Springer Tracts in Modern Physics,2009, vol. 231.

[14] J. Ziegler, SRIM-2011 [Online]. Available: www.srim.org[15] E. Fred, LEDBasics: Electrical Properties in Light-EmittingDiodes.

Cambridge, U.K.: Cambridge Press, 2006.[16] S. M. Lee, S. H. Sung, M. M. Marton, S. S. Perry, and J. W. Rabalais,

“Annealing effect on the surface morphology of Si(100),” in Proc. 11thInt. Conf. Ion Implant Technology, 1997, pp. 650–653.

Fabrication and characterization of ultra-thin magnetic films for biomedical applications

Documents

Transcript of Fabrication and characterization of ultra-thin magnetic films for biomedical applications