Optimization of electron beam focusing for gated carbon nanotube field emitter arrays

2584 IEEE TRANSACTIONS ON ELECTRON DEVICES, VOL. 52, NO. 12, DECEMBER 2005

Optimization of Electron Beam Focusing for GatedCarbon Nanotube Field Emitter Arrays

Jun Hee Choi, Andrei R. Zoulkarneev, Young-Jun Park, Deuk Seok Chung, Byung Kwon Song, Ho Suk Kang,Chan Wook Baik, In Taek Han, Ha Jin Kim, Mun Jin Shin, Ha Jong Kim, Tae Shik Oh, Yong Wan Jin,

Jong Min Kim, and Naesung Lee

Abstract—We fabricated gated field emitter arrays with a novelfocusing structure of electron beams, where the focusing electrodeconcentrically surrounded each gate hole. Carbon nanotube emit-ters were screen printed inside an amorphous-Si concave well farbelow the gate. It was theoretically and experimentally verified thatthe concave well structure effectively focused the emitted electronbeams to their designated phosphor pixels by modulating focusinggate voltages. For the vacuum packaged field emission displayswith the pixel specification fitting high-definition televisions, colorreproducibility of approximately 71% was achieved at the bright-ness of 400 cd/m2.

Index Terms—Carbon nanotube (CNT), electron-beam (e-beam)focusing, field emitter arrays.

I. INTRODUCTION

SCREEN-PRINTED carbon nanotube field emission dis-plays (CNT-FEDs) have belonged to the main currents of

FEDs, together with the surface-conduction electron emitterdisplays (SEDs) [1]–[5]. Both displays have the commonfeature that they are fabricated with thick-film printing tech-nologies, which are applicable to high-definition televisions(HDTVs). One of the critical issues in the SEDs is to enhancethe efficiency of emitted electrons (the ratio of the number ofelectrons going to the anode to the total number of emittedelectrons) currently as low as about a few percents for highbrightness. Although the high anode currents can be easilyachieved for the CNT-FEDs, on the other hand, the electron-beam (e-beam) focusing is to be improved for high colorreproducibility.

Emitted e-beams can be focused in FEDs, in most cases, byintroducing an additional electrode on gated field emitter arrays(FEAs). This corresponds to a single-aperture electrostatic fo-cusing lens. The focusing electrode is usually grounded or neg-atively biased such that the electrode repels diverging e-beamsto the central axis for their focusing to designated phosphorpixels. Recently, we reported the e-beam focusing structure forthe gated FEAs where one focusing gate (FG) enclosed sev-eral gate holes [6]. In this structure, however, e-beams fromall the gate holes could not be well focused since a different

Manuscript received April 20, 2005; revised August 23, 2005. The review ofthis paper was arranged by Editor H.-S. Tae.

J. H. Choi, A. R. Zoulkarneev, Y.-J. Park, D. S. Chung, B. K. Song, H. S. Kang,C. W. Baik, I. T. Han, H. J. Kim, M. J. Shin, H. J. Kim, T. S. Oh, Y. W. Jin, andJ. M. Kim are with the Materials Laboratory, Samsung Advanced Institute ofTechnology, Suwon, Korea (e-mail: [email protected]).

N. Lee is with the Department of Nano Science and Technology, Sejong Uni-versity, Seoul, Korea.

Digital Object Identifier 10.1109/TED.2005.859595

distance between the FG and each gate hole resulted in a dif-ferent focusing force to the e-beams from each hole. Thus, wedevise that each gate hole is concentrically surrounded by eachFG hole so that the e-beams from all CNT dots can experiencesymmetrical electric fields from the FG. The former and thelatter structures are called as hole-to-multi-hole (HTMH) andhole-to-hole (HTH) structures, respectively. In FEAs with HTHstructure, the electrode configuration of cathode is also modi-fied to have a concave well where the CNT emitters are formedinside to improve e-beam focusing. This study experimentallymeasured and simulated the e-beam focusing characteristics ofthe HTMH, the HTH nonconcave, and HTH concave structures,for vacuum-packaged FED devices. Here we report a novel fo-cusing FEA structure having a very robust focusing capabilityof e-beams.

II. EXPERIMENTAL

We fabricated 5-in diagonal-gated FEAs with the previouslyreported HTMH structure [6], and the HTH nonconcave andconcave structures to focus e-beams (see Fig. 1). Our FEAs, inspite of their size of 5-in diagonal, were designed to have thesame pixel specification as that of large area (38 in) high-def-inition televisions (HDTVs). Their fabrication processes weredescribed in detail elsewhere [7]. Resistive amorphous-Si (a-Si)and insulating SiO layers were deposited by radio-frequencyplasma enhanced chemical vapor deposition. The 1- m-thicka-Si:H layer was etched out to form the concave in the HTHstructure. In order to ensure equi-potential contours near thea-Si:H layer to follow the outline of the concave, the electricalresistivity of the a-Si:H layer was controlled as low as 300 cmby controlling SiH PH ratios. The a-Si:H layer also acted asa ballast between the cathode electrode and the CNT emitters,which has the resistance of 15 k in the HTH concave struc-ture. The nonconcave HTH structure was also fabricated to com-pare their focusing characteristics of e-beams. For all structures,the thicknesses of a gate insulating layer (GI) and a FG insu-lating layer (FGI) were 3 and 6 m, respectively. These layerswere composed of low-density SiO , which was designed tohave as a high etching rate as 0.6 m/min and as a low film stressas 50 MPa by controlling SiH N O ratios. In the HTH struc-ture, a 50- m-diameter circular FG hole encompassed a 16- m-diameter gate hole, which in turn surrounded a 10- m-diameterCNT dot. After completing the structures, single-walled CNTdots were formed inside the gate holes by a series of processes:screen printing a photosensitive CNT-containing paste, illumi-nating an ultraviolet (UV) light backside through circular a-Si

0018-9383/$20.00 © 2005 IEEE

CHOI et al.: OPTIMIZATION OF ELECTRON BEAM FOCUSING FOR GATED CARBON NANOTUBE ARRAYS 2585

Fig. 1. Plan and cross-sectional (x � x ) view schematics of (a) HTMH,(b) HTH nonconcave, and (c) HTH concave structures.

holes with the 10- m diameter, and developing the UV-exposedCNT paste [8]. CNTs were then fired at 450 C in an N am-bient, and the surface activation process was finally performedto get active CNTs participating for field emission [8]. In theconcave HTH structure, the activation process was optimizedsuch that the heights of most CNTs in the concave holes werekept lower than the top level of the a-Si layer [see Fig. 2(b)].Field emission properties and e-beam focusing capability of ourFEAs both in a vacuum chamber and in vacuum packaged de-vices were measured under the spacer gap of 1.5 mm between ananode plate and a cathode plate. E-beam focusing was charac-terized by measuring the CIE chromaticity coordinates of R, G,and B, colors, when each color was turned on in the packagedFED panels. We also carried out computer simulations usingcommercial codes of SIMION (Scientific Instrument Services)to investigate e-beam trajectories. The calculations were pro-ceeded by assuming the beam divergence range and the energyof electrons launched from CNTs to be 90 90 and 5 eV,respectively.

III. RESULTS AND DISCUSSION

We fabricated the FEAs with the HTMH structure for e-beamfocusing, as shown in Fig. 2(a), where a rectangular-shaped FGsurrounds seven gate holes [6]. In the HTMH structure, the long(x) and short (y) axes of the FG rectangle shown in Fig. 1 corre-spond to cathode and gate lines, respectively, which cross per-pendicularly each other. The e-beams launched from the seven

Fig. 2. Tilted and cross-sectional SEM images of the FEAs with (a) the HTMHnonconcave structure and (b) the HTH concave structure.

gate holes enclosed by the same FG rectangle are desired to ar-rive at just only one color pixel. Fig. 3 shows e-beam trajec-tories for CNT dots located inside just one HTMH structure.The simulations were carried out for the cross section along thelong axis (x axis) of the HTMH rectangle such that three phos-phor pixels on the anode in Fig. 3(a) belong to the same color.Comparing the simulations and the experimental observationsof e-beam spreading, we found that an initial energy and diver-gence angles of e-beams at the moment of emission from CNTswere 5 eV and 90 90 , respectively [6]. It seems thatsuch a wide e-beam divergence of 90 90 results fromrandom orientation of CNT emitters inside a gate hole. Subjectto a certain bias (negative voltages for e-beam focusing), as dis-tinctly seen in Fig. 3(b) and (c), the FG would form equipo-tential contours around it, giving rise to electrostatic forces re-pelling e-beams toward the z axis. Farther away from the FG,a magnitude of this focusing force becomes smaller. In Fig. 3,therefore, the e-beams emitted from the gate hole nearest to theFG are most sharply deflected by the FG voltage , whilethose from the second- and the third-nearest gate holes are lessand less affected. Even the e-beams from the nearest gate holeshow asymmetric deflection on the upper and lower sides, due todifferent distances from the FG. The e-beams from the nearestgate hole are well focused to the designated phosphor pixel, butthose from the second and third holes are under-focused to reachthe neighboring pixels, thus degrading the color purity of a FEDdevice. In the HTMH structure, a different distance between theFG and each gate hole results in a different focusing force tothe e-beams from each hole. In addition, the rectangular shapeof the HTMH aperture would results in asymmetric focusing ofthe e-beams along the long (x) and short (y) axes of the struc-ture. Conclusively, it is desired that the FG gives rise to identical,symmetric equi-potential contours around each gate hole.

To address this problem, we devised each round gate holeto be concentrically enclosed by its own circular FG such thate-beams from all CNT dots experience the identical, symmetric


Fig. 3. Simulation of e-beam trajectories for the FEAs with the HTMHfocusing structure. (b) and (c) show magnified views of (a). In (a), the x axisruns along a cathode (data) line, corresponding the long axis of the HTMHstructure, such that three phosphor pixels have the same color. In (a), onlythree out of seven gate holes in a HTMH structure were considered due to theirsymmetric nature. Simulations were carried out at V = 2:5 kV, V = 80 V,and V = �40 V with the spacer gap of 1.5 mm.

electric fields from the FG. It is thus called as the HTH structure.Fig. 1(b) and (c) show two different types of HTH structuresequipped to the FEAs. In Fig. 1(b), the CNT dot is put on a flatcathode surface. Here, the CNT dot almost reaches the gate inheight, but never exceeds. (The right-hand figure of Fig. 2(a)corresponds to the cross-sectional view of HTH nonconcave orHTMH nonconcave structure.) The other HTH structure givenin Fig. 1(c) reveals that the CNT dot is formed inside a concavewell, which was fabricated by etching out the a-Si layer. It isnoted that the most CNTs in the concave well are maintainedlower than the height of the well and are thus far below the gate[see Fig. 2(b)]. By considering their structural characteristics,the former and latter are called here as the HTH nonconcaveand concave structures, respectively.

For both structures, we simulated the equi-potential lines andthe resultant e-beam trajectories, as given in Fig. 4, on the crosssection along the short axis (y axis) of a phosphor pixel. Thus,three phosphor pixels on the anode have different colors. Here,

Fig. 4. Simulation of e-beam trajectories for the FEAs with (a) and (b) theHTH nonconcave structure and (c) and (d) the HTH concave structure fore-beam focusing. (b) and (d) are magnified views of (a) and (c), respectively.Here, three phosphor pixels on the anode correspond to different colors.Simulations were carried out at V = 2:5 kV, V = 80 V, and V = �40 Vwith the spacer gap of 1.5 mm.

the same initial energy and divergence angles of e-beams asthose of Fig. 3 were used as well. Once e-beams are emittedfrom the CNTs with wide spreading angles, their trajectorieswould be determined by a spatial distribution of equi-potentiallines produced by a gate voltage , , and an anode voltage

. In the HTH nonconcave structure where a metallic CNTdot is put on an electrically grounded, flat cathode surface, theequi-potential lines become convex above the metallic dot alongits outline due to its protruding shape, whatever the magnitudesof , , and are [see Fig. 4(b)]. In such spatial distribu-tion of potential contours, the e-beams launched near the gateare more diverged from the z axis and approach more closelythe FG. The e-beams coming closer to the FG would be morestrongly affected by . In the simulation, the most widelyspreading e-beams are reflected even back to the gate and thesecond widely spreading e-beams are strongly deflected acrossdown the z axis and are over-focused to reach the unwantedneighboring pixel which is a different-color phosphor in thiscase. In the simulations for the smaller magnitude of (notshown here), such an over-focusing could be avoided, but, on thecontrary, some e-beams were under-focused to hit other pixels.In the HTH focusing structure with CNT dots formed a flatcathode surface, therefore, the e-beams could not be well fo-cused to their destinations. The simulation suggests that the poorfocusing is ascribed to wide spreading of e-beams from the CNTdot inside each gate hole.

Fig. 4(c) and (d) shows the equi-potential lines and the e-beamtrajectories of the FEAs with the HTH concave structure. Theequi-potential lines run parallel along the a-Si surface outsidethe concave, but some low-voltage potential lines are curved in-ward at the concave well. Other high-voltage lines are curvedoutward, but much less inclined, compared with the nonconcavecase. If e-beams are emitted below the top level of the a-Si well,therefore, their divergence would be greatly reduced. These less-spreading e-beams are once again focused by the FG. Our FEAswith the HTH concave structure lead all e-beams to their corre-sponding phosphor pixels, as shown in Fig. 4(c).


Fig. 5. CCD-magnified pixel images of the FEAs having the HTH concavestructure on the nonpatterned green phosphor at different V s of (a) 0 V, (b)�5 V, (c) �10 V, and (d) �15 V, all under V = 2.5 kV, V = 80 V, and thespacer gap of 1.5 mm.

Fig. 6. SEM images of CNT emitters inside the HTH concave structure,showing abnormally long CNTs extended above the top level of the a-Siconcave.

We investigated the focusing capability of our FEAs havingHTH concave structure by observing the pixel images. Fig. 5 ex-hibits CCD images of pixels at different ’s. A nonpatternedgreen phosphor was used to straightforwardly reveal an extentof e-beam focusing. At equal to 0 V, pixels are overlappedtogether not to be clearly distinguished. Each pixel is here com-posed of superposed circular emission spots. At 5 V, the pixelsstart to be distinctly discerned and, at 10 V, they are furtherseparated each other such that a lateral pixel-to-pixel gap isas wide as a pixel. At 15 V, the pixels are more shrunk andsome fringes occur between pixels. As becomes negativelylarger down to 30 40 V, the fringes are more apparentlydeveloped, which implies that the fringes are attributed to theover-focused e-beams. In our simulation on the concave struc-ture, however, the over-focusing of e-beams did not appear at

of 40 V, as given in Fig. 4. Abnormally long CNTs areoccasionally observed to be protruding over the top level of thea-Si well, as seen in Fig. 6. The emitter tips of such long CNTswould be exposed to outward-curved equi-potential lines in theconcave in Fig. 4(d). In this case, the e-beams would follow thetrajectories of Fig. 4(a) and (b) rather than those of Fig. 4(c)

Fig. 7. (a) and (c) White-color brightness and (b) and (d) color reproducibilitywithV of the FEAs with the HTH concave [(a), (b)] and HTH nonconcave [(c),(d)] structures, at the constant V of 4 kV and the constant I s of 100, 300, and500 �A. Here, I was controlled by V at the constant V and the spacer gapwas 1.5 mm.

and (d), being over-focused to the neighboring pixels. More finecontrol of CNT lengths is currently under investigation.

After vacuum packaging of FED devices, the brightness andthe e-beam focusing with were studied for the FEAs with theHTH concave [Fig. 7(a) and (b)] and nonconcave [Fig. 7(c) and(d)] structures. The devices were installed with patterned colorphosphors with black matrices between pixels. Here, the e-beamfocusing was measured with color reproducibility (CR), whichis defined as a ratio of the triangular area made by R, G, B colorcoordinates of a FED device to that made by coordinates of threeindividual phosphors themselves. The former coordinates weremeasured by turning on each color on a patterned R, G, B phos-phor plate of the packaged device, while the latter coordinateswere recorded using nonpatterned, R, G, B each-color phosphorplate. For the HTH concave structure, as shown in Fig. 7(a), thebrightness increases with getting more negative down to

40 V, measured at three different anode currents for givenanode voltages of 4 kV. In Fig. 7(b), their correspondingCRs are also varied with in the same manner as that of thebrightness. The CR is saturated above of 30 V for all .In particular, the CR reaches 92% at of 40 V forof 100 A. At a higher (controlled by ), the brightnessincreases, but the CR decreases probably due to the wider di-vergence of e-beams. In Fig. 5, the over-focused beams start tooccur at 15 V, but here in Fig. 7(b), the CR is improved with

even down to 30 V. Such a disagreement may be explainedin the following manner. More negative biasing of increasesthe intensity of e-beams focused to the designated phosphorpixel, but simultaneously produces more over-focused e-beamsto the neighboring pixels. It seems that the former contributionexceeds the latter, overall improving the CR with more negative

. For the HTH nonconcave structure, on the other hand, themaximum brightness and the maximum CR are obtained atof 10 V, as shown in Fig. 7(c) and (d), probably due to largerover-focusing of e-beams at more negative .


Fig. 8. Color reproducibility versus white-color brightness of the FEAs with(a) the HTH concave and (b) the nonconcave structures. The brightness wascontrolled by varying V . Measurements were performed at V = 80 V andV = �40 V with the spacer gap of 1.5 mm.

For the FEAs with the HTH concave and nonconcavestructures, the CR was measured versus white-color bright-ness, as given in Fig. 8. The measurements were carried outfor the vacuum-packaged FED devices having the patternedcolor-phosphor plate coated with the 50-nm-thick Al reflectionlayer. The higher brightness was recorded at higher . At thewhite brightness of 400 cd/m , which is usually required forTV applications, the CR reaches 71% for the HTH concavestructure, whereas only 65% for the nonconcave structure.For both structures, in Fig. 8, the CR decreases as the brightnessincreases. These observations are contrary to our expectationthat the e-beams are more focused with increasing , whichhas been confirmed in the computer simulations. One of thepossible explanations is light reflection from the shiny FG sur-face. This issue is now under investigation, by using a thickerAl reflection layer coated on the phosphor screen and also byblackening the FG surface, both to reduce the light reflection.Another possibility is as follows. As is increased, the numberof unfocused electrons onto the neighboring phosphor pixels isreduced (because more e-beams are focused onto the designatedpixel), but they collide more energetically with the phosphors.Thus, an increase of improves the CR by decreasing thenumber of unfocused electrons, but simultaneously deterioratesit by increasing their collision energy. If the latter contributemore strongly than the former, the CR would become worse athigher , but this hypothesis has to be verified.

Fig. 9 shows measured as a function of , , andfor our FEAs with the HTH concave structure. In Fig. 9(a),exponentially increases with , but a higher is obtained at ahigher [also in Fig. 9(b)]. Desirably, should be unaffectedby changing for triode-type FEAs, but not in this case. Thisis because the electric fields from the anode are not completelyshielded by the gate or the FG electrode to have an influence onthe emission of CNTs. Fortunately, however, the turnon ismaintained at 35 V irrespective of changing the from 1000to 2000 V. It implies that our device can be successfully operatedby setting the turn-off and -on to 35 and 70 V, respectively,under the of 1000 2000 V. In particular, the device is com-pletely turned off at 35 V without the background emission,so-called diode emission. Such a diode emission did not occurat of 35 V up to of 6 kV for the spacer gap of 1.5 mm inour devices. For reference, our packaged devices with the 1.1,1.5, and 2.0 mm gaps worked at 3.5, 6, and 8 kV without sucha diode emission or electrical arcing, respectively. An applica-

Fig. 9. I measured as a function of (a) V and (b) V at different V s forthe FEAs with the HTH concave structure. Both were measured using a spacergap of 1.5 mm and V of �40 V, and V of 80 V in (a) and (b), respectively.In (a), the dotted and solid lines represent theoretical I -V curves at the V of1000 and 2000 V, respectively, calculated by considering the Fowler–Nordheimrelationship and a resistive voltage drop across the resistive layer.

tion of a high is inevitable in FEDs to achieve long lifetime,good color reproducibility, low power consumption, etc. It isworth noting that our devices with the HTH concave structureare quite well immune to electric arcing sometimes induced bysuch a high . For example, the electric arcing rarely occurredup to 8 kV for the 2-mm gap. Even if the arcing happened, therewas little damage to our devices, likely because the metallic FGcovering most of the active area of a cathode plate acted as a sup-pressor or an absorber of the arcing by effectively dissipatingthe electrical charges which might be built up in the insultingsurface [9].

Fig. 9(a) and (b) gives that is strongly affected by aswell as and . It is implied that all the electric fields fromthe gate, the FG, and the anode are superimposed to simultane-ously act at the CNT tips and contribute to their electron emis-sion. When the electrons are emitted from CNTs by betweengate and cathode electrodes, an actual voltage difference be-tween the emitters and the gate line is smaller than due to


a voltage drop at an in-between resistor. An a-Si layer is com-monly used as a ballast between emitters and the cathode line inFEDs to improve their brightness uniformity [10]. The ballastreduces excessive emission currents from pixel to pixel, leadingto quite linear dependence of on or , as observed inFig. 9. In our case, the resistance of the a-Si layer usedwas experimentally measured to be 15 k . Neglecting a gateleakage current (in our case, estimated to be less than 5% of

), the emission current from the CNTs is assumed to be thesame as , and thus can be expressed by

(1)

The voltage difference between the focusing gate and theCNT emitters can also be expressed in the same manner

(2)

For , it is assumed that the voltage drop of is negligiblecompared to the large magnitude of .

By superimposing electric potentials of each electrode usingthe SIMION software, we attained an electric field E in the cen-tral position 1 m above from the cathode line

V/cm (3)

As expected, the gate voltage makes the largest contribution tothe electron emission from the CNTs. It is noted that the FGis negatively biased in most cases. Subject to the electric fieldgiven by the (3), the CNT emitters would result in an emissioncurrent , following the Fowler–Nordheim relationship [11]:

1.4 10 6.53 10(4)

where , , and are an effective emission area, a field enhance-ment factor, and the work function of CNTs ( 5 eV [12]), re-spectively. From (1) to (4), curves of with are numericallycalculated by varying , , and R at different , until differ-ences between the calculated and measured reach minima.The best-fitting, calculated – curves are given in Fig. 9(a),when , , and are 2.39 10 cm , 1220, and 12 k , re-spectively. Curves of - , and - could also be calculatedin the same manner. This algorithm can extract true Fowler–Nordheim I–V curves from those of FEAs with a ballast resis-tive layer.

IV. CONCLUSION

We demonstrated three different FG structures for the e-beamfocusing in the gated FEAs. The e-beams were under-focused inthe HTMH structure, but over-focused in the HTH nonconcavestructure. The HTH concave structure, however, accurately fo-cused almost all e-beams to their corresponding phosphor pixelsunder the optimum operation condition. The highest color repro-ducibility was obtained at of 30 40 V. Our vacuumpackaged FED panels, whose pixel specification was designed

to fit large area, HDTVs, achieved the color reproducibility of71% at 400 cd/m . In comparison between the theoretical and

measured I–V curves, the calculated ballast resistance of the a-Silayer agreed well with its measured one. It is also noted that theFEAs with the HTH concave structure are fairly immune to elec-tric arcing even at a high .

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Jun Hee Choi received the B.S. degree in ceramic engineering from YonseiUniversity, Seoul, Korea, in 1992 and the M.S. degree in materials science andengineering from Korea Advanced Institute of Science and Technology, Dae-jeon, Korea, in 1994.

He has been developing various FEAs such as Spindt-type, etch-type, andCNT-based FEAs at the Samsung Advanced Institute of Technology (SAIT),Suwon, Korea, since 1994. His research activities are currently focused upon theoptimization of FEA structures for electron beam focusing and the enhancementof display images in the CNT FEDs.

Andrei R. Zoulkarneev received the B.S. and M.S. degrees in radio-physicsand electronics from the Saratov State University, Saratov, Russia, in 1975 and1977, respectively, and received the Ph.D. degree in microelectronics sciencesfrom R&D Enterprise "Almaz," Saratov, in 1989.

From 1989 to 1994, he had been the Laboratory Director of electron beamlithography and submicron technology in the R&D Enterprise "Almaz." In1994, he joined the Samsung Advanced Institute of Technology (SAIT), Suwon,Korea, to develop FEDs. His present research interests include the synthesisof thin films such as an insulation layer and a resistive layer by PECVD andthe computer simulation of FEA structures and corresponding electron beamtrajectories for FEDs.


Young-Jun Park received the B.S. and M.S. degrees in physics from SogangUniversity, Seoul, Korea, in 1990 and 1992, respectively, and the Ph.D. degreein nanoscience and technology from Sungkyunkwan University, Suwon, Korea,in 2003.

He joined the Samsung Advanced Institute of Technology (SAIT), Suwon,Korea, in 1992. He has worked on the synthesis of advanced thin film materialsand fabrication processing of optical display devices and FEDs. His current re-searches are focused on the synthesis and functionalization of CNTs, nano com-posite materials, and integration of displays and low-cost, high-efficiency solarcells.

Deuk Seok Chung received the B.S. degree in materials science and engi-neering from Inha University, Inchon, Korea, and the M.S. degree in materialsscience and engineering from Seoul National University, Seoul, Korea, in 1995and 1997, respectively. He is currently pursuing the Ph.D. degree in nanoscienceand technology at Sungkyunkwan University, Suwon, Korea.

He is presently working at the Samsung Advanced Institute of Technology(SAIT), Suwon, Korea. His main concern is the synthesis and characterizationof CNT pastes and the fabrication processes of field emission devices.

Byung Kwon Song received the B.S. and M.S. degrees in physics from HanyangUniversity, Seoul, Korea, in 1998 and 2000, respectively. He is currently pur-suing the Ph.D. degree at Hanyang University.

He is with the Samsung Advanced Institute of Technology (SAIT), Suwon,Korea. His research interests are put on vacuum packaging of CNT FEDs andbacklight units (BLUs) for liquid crystal displays

Ho Suk Kang received the B.S. and M.S. degrees in physics from HanyangUniversity, Seoul, Korea, in 1999 and 2001, respectively.

He has been developing flat panel displays and nano materials at the SamsungAdvanced Institute of Technology (SAIT), Suwon, Korea, since 2002.

Chan Wook Baik received the B.S., M.S., and Ph.D. degrees in physics fromSeoul National University, Seoul, Korea, in 1997, 1999, and 2004, respectively.During the Ph.D. studies, his interest was on the investigation of beam-waveinteraction mechanism in cyclotron harmonic operation, and he developed athird-harmonic frequency-multiplying gyro-TWT amplifier.

From 1997 to 2004, he was involved in the development of coherent radiationsources, such as klystrons, magnetrons, gyrotrons, and helix-TWTs. Since hejoined the Samsung Advanced Institute of Technology (SAIT), Suwon, Korea,in 2004, both his theoretical and experimental studies have been on terahertz-radiation sources including field emission devices based on CNTs are his currentresearch interests.

Dr. Baik received the IVEC Student Paper Award at the 2004 InternationalVacuum Electronics Conference (IVEC) in Monterey, CA.

In Taek Han received the B.S., M.S., and Ph.D. degrees in chemistry from SeoulNational University, Seoul, Korea, in 1989, 1991, and 2005, respectively.

Since joining the Samsung Advanced Institute of Technology (SAIT), Suwon,Korea, in 1995, he has been engaged in the development of FEDs and the CVDsynthesis of CNTs and their applications to electronics such as FEDs and semi-conductors.

Ha Jong Kim received the B.S. degree in electronics engineering fromKyungwon College, Sungnam, Korea.

He has been working as a Process Engineer to develop CNT FEAs at SAIT,Suwon, Korea, since 2001.

Mun Jin Shin received the B.S. degree in Electronics Engineering fromDuwon College, Ansung, Korea. He has been working as a technician forvacuum packaging of FEDs in the Samsung Advanced Institute of Technology(SAIT), Suwon, Korea, since 2002.

Ha Jin Kim received the B.S. and M.S. degrees in materials engineering fromSungkyunkwan University, Suwon, Korea, in 1999 and 2001, respectively.

He has been working on CNT FEDs at the Samsung Advanced Institute ofTechnology (SAIT), Suwon, Korea, since 2001.

Tae Shik Oh ntreceived the B.S. degree in electronics from Sungkyunkwan Uni-versity, Suwon, Korea, the M.S. degree in electronics from Kyunghee Univer-sity, Suwon, Korea, and the Ph.D. degree in nanoscience and technology fromSungkyunkwan University in 1985, 1990, and 2005, respectively.

He joined Samsung SDI, Suwon, Korea, in 1984 and then moved to the Sam-sung Advanced Institute of Technology (SAIT), Suwon, Korea, in 2003. Heis currently researching computer simulation for FEDs, organic light-emittingdiodes, and organic thin-film transistors.

Yong Wan Jin received the B.S. degree in chemical engineering from YonseiUniversity, Seoul, Korea, the M.S. degree in chemical engineering from KoreaAdvanced Institute of Science and Technology, Daejeon, Korea, and the Ph.D.degree in materials engineering from Sungkyunkwan University, Suwon, Korea,in 1987, 1990, and 2002, respectively.

His main research interests are centered upon the developments of variousflat-panel display devices and CNT composite materials.

Jong Min Kim received the B.S. degree in electronics engineering from HongikUniversity, Seoul, Korea, in 1980, and the M.S. and Ph.D. degrees in electricalengineering from the New Jersey Institute of Technology, Newark, in 1992.

He was with the Army Research Laboratory, Research Triangle Park, NC,from 1992 to 1994, and joined the Samsung Advanced Institute of Technology(SAIT), Suwon, Korea, in 1994. Since then, he has been in charge of the de-velopment of microtip FEDs and CNT FEDs. As a Vice President, he is alsocurrently in charge of the Display Laboratory and Materials Center.

Dr. Kim became "Samsung Fellow" in 2003, which is awarded to the mostoutstanding researchers at SAIT.

Naesung Lee received the B.S. degree from Seoul National University, Seoul,Korea, the M.S. degree in materials science and engineering from Korea Ad-vanced Institute of Science and Technology, Korea, and the Ph.D. degree in ma-terials science and engineering from Pennsylvania State University, UniversityPark, in 1984, 1986, and 1996, respectively.

He had been working on microtip FEDs and CNT FEDs at the Samsung Ad-vanced Institute of Technology (SAIT), Suwon, Korea, from 1997 to 2001. Heis now with Sejong University, Seoul, where he has carried out research that in-cludes the CVD synthesis of CNTs and their applications mainly to field emit-ters, nanoelectronics, nanocomposites, etc.

Documents

Optimization of electron beam focusing for gated carbon nanotube field emitter arrays