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1 Synthesis and structural analysis of nano-semiconductor material

2 Synthesis and structural analysis of nano-semiconductor material

4 (1) MOCVD ZnO (2) MOCVD gallium oxide < gallium oxide > < gallium oxide >

5 (3) Thermal evaporation gallium oxide (4) MOCVD 1 indium oxide

6 Abstract (1) Synthesis of ZnO nanorods by an MOCVD system The ZnO nanorods have synthesized on Si(100) substrates without a metal catalyst by a reaction of a diethylzinc (DEZn) and oxygen (O 2 ) mixture. At a substrate temperature of 450, the growth structure has changed from clusters to nanorods with increasing Ar/O 2 gas flow ratio. The ZnO nanorods had an average diameter of nm, and transmission electron microscopy (TEM) showed a single crystalline structure. (2) Synthesis of gallium oxide nanowires by an MOCVD system < Single crystal gallium oxide nanowires> The monoclinic gallium oxide (β-ga 2 O 3 ) nanowires have synthesized on Au-coated Si substrates by a reaction of a trimethylgallium (TMGa) and oxygen (O 2 ) mixture. The β-ga 2 O 3 nanowires became progressively thinner from bottom to top, with diameters ranging from 10 to 200 nm and lengths of several micrometers. We found that Au-containing nanoparticles were attached to the tips of β-ga 2 O 3 nanowires and thus the nanowire growth could be a vapor-liquid-solid (VLS) process. < Amorphous gallium oxide nanowires> The large-scaled gallium oxide nanowire arrays have prepared on Si(100) substrates using a reaction of a trimethylgallium (TMGa) and oxygen (O 2 ) mixture. The cross-section of the gallium oxide

7 nanowires had a circular shape with the diameter of about nm. Transmission electron microscopy and x-ray diffraction analysis together showed that the nanowires were amorphous phase. (3) Synthesis of gallium oxide nanobelts by thermal evaporation The production of gallium oxide (Ga 2 O 3 ) nanobelts demonstrated on various substrates by thermal evaporation of GaN powders. Scanning electron microscopy revealed that the product consisted of nanobelts with widths in the range of nm. X-ray diffraction and high-resolution electron microscopy indicated that the nanobelts were single-crystalline monoclinic structure of Ga 2 O 3. The photoluminescence spectrum under excitation at 325 nm showed a broad band with a prominent emission peak around 433 nm. (4) Catalyst-free MOCVD growth of In 2 O 3 one-dimensional materials One-dimensional (1-D) indium oxide (In 2 O 3 ) arrays have succeeded in synthesizing by metalorganic chemical vapor deposition (MOCVD) method. We have characterized the products by means of X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), and transmission electron microscopy (TEM). SEM images showed that the 1-D materials with the serrated surfaces had the cross sections of acute triangle. XRD and TEM studies revealed that the 1-D materials possessed single-crystalline cubic structure and had preferentially grown along the [111] direction.

16 p x = 2 h 2π h 2 2 p ( k) E = = k 2µ 2µ µ

17 E = E π 1 1.8e + 2 2r µ ε r 2 2 r ε2

18 (a) 0-demension nanorod nanowire nanotube nanocable nanobelt (b) 1-demension (c) 2-demension Fig 2-1. The type of nanomaterials

48 Fig Schematic drawing of MOCVD system.

49 (a) (b) (c) 200nm 200nm 200nm Fig Plan-view SEM images of ZnO deposits grown at 450 with Ar/O 2 gas flow ratio (a) 0.3, (b) 1 and (c) 4.

50 (a) (b) Si substrate Fig Cross-sectional SEM images of ZnO nanorods at 450C with Ar/O 2 gas flow ratio (a) 1 and (b) 4.

51 Intensity (arb. units) θ (deg.) Fig XRD patterns recorded from deposits

(a) (b) 001 100 50nm [010] 100nm Intensity (arb. units) (c) C Zn O Cu Zn Zn 0 2 4 6 8 10 Energy (kev) Fig 3-5.

52 (a) (b) nm [010] 100nm Intensity (arb. units) (c) C Zn O Cu Zn Zn Energy (kev) Fig 3-5. Bright field TEM images of (a) ZnO nanorods grown on the Si substrate and (b) a ZnO nanorod (the inset shows corresponding SAED pattern recorded along the [010] zone axis). (c) Typical EDS spectrum of a ZnO nanorod ( the Cu and C peaks come from the supporting carbon-coated copper grids in TEM sample preparation).

53 (a) (b) Fig 3-6. SEM images of ZnO deposits grown at 400C (a) plan-view (b) cross-sectional

54 (a) (b) Fig 3-7. Growth mechanism of the ZnO nanorods grown by MOCVD system without catalyst (a) reality and (b) ideal.

60 (a) (b) (c) (d) (e) (f) Ga 2 O 3 thin film Fig SEM images of gallium oxide deposits grown on Si(100) substrate at 600C when Ar carrier gas flow rate is 30sccm and O 2 gas flow rate is (a,b) 0sccm, (c,d) 6sccm, (e,f) 10sccm.

62 (a) (c) (e) (b) (d) (f) Fig SEM images of gallium oxide nanowires grown on Si(100) substrate at (a) 600C, (b) 650C, (c-f) 700C when Ar carrier gas flow rate is 30sccm and O 2 gas flow rate is 6sccm.

63 θ (deg.) Intensity (arb. units) Fig X-ray diffraction patterns recorded from Ga 2 O 3 nanowires.

64 (a) (b) 500nm 100nm (c) Intensity (arb. units) C Ga O Cu Ga Cu Ga Energy (kev) Fig TEM characterization of the Ga 2 O 3 nanowires. (a) Low magnification TEM image. (b) High resolution TEM image (inset : corresponding electron diffraction pattern). (c) EDS spectra of the nanowire.

65 Fig Growth mechanism of the Ga 2 O 3 nannowires grown by MOCVD system without catalyst.

66 (a) (b) Fig (a) Plan-view and (b) side-view SEM images of the deposited nanowires.

67 β θ (deg.) Intensity (arb. units) Fig X-ray diffraction patterns recorded from the Ga 2 O 3 nanowires

68 (a) 100nm (c) C O Ga Au Tip Cu Cu Ga (b) Amorphous layer 10nm d=0.46nm (102) C O Ga Energy (kev) Stem Fig (a) TEM and (b) HRTEM images of a single β-ga 2 O 3 nanowire. The nanowire terminates with a nanoparticle. (c) EDS spectra of the nanowire tip and the nanowire stem. Cu Cu Ga

69 1

70 Fig Growth mechanism of the Ga 2 O 3 nannowires using Au catalyst by MOCVD system.

71 β

76 4 GaN ( s ) 4 Ga ( g ) + 2 N 2( g ) Ga( s) + 3O ( g) 2Ga O ( ) s Upper holder Out Heating units Distance (5mm) Substrate GaN powder N 2 In Lower holder Themocouple Fig Schematic drawing of thermal furnace system.

77 Intensity (arb. units) 004 or θ (deg.) Fig XRD pattern of the as-deposited products on Si(100) substrate

78 Ǻ Ǻ Ǻ (a) (b) (c) (d) 2nm Si(100) Fig (a),(b),(c) SEM and (d) TEM images showing ther general morphology of as-deposited products. (a) plan-view image, (b) side-view image, (c) high-magnification image and (d) high resolution images.

79 (a) (b) (c) (d) Fig SEM images of gallium oxide deposits using Ir catalyst. Gallium oxide deposits grown at (a),(b) 900C and (c),(d) 970C.

80 970 C 900 C Wavelength (nm) Fig Room temperature PL spectra of the products at growth temperatures of 900 º C and 970 º C with an excitation wavelength of 325 nm. Intensity (arb. units)

81 (a) (b) nm 500nm [121] (c) 101 2nm Fig (a) TEM image of Ga 2 O 3 nanobelts. (b) TEM image of a β- Ga 2 O 3 nanobelt. The inset shows the corresponding SAED pattern recorded. (c) HRTEM image.

82 Intensity (arb. units) β-(004) β-(104) β-(202) β-(111) β-(111) Ir-(111) GaIr-(110) β-(113) β-(213) Ir-(200) θ (deg.) Fig XRD pattern of the as-deposited products on Pt-coated SiO 2 substrate at 900 º C

83 (a) (b) Fig SEM images of gallium oxide deposits using Pt catalyst. (a) Side-view image and (b) high-magnification image of gallium oxide deposits at 900C

84 Wavelength (nm) Intensity (arb. units) Fig Room temperature PL spectrum of the products with an excitation wavelength at 325nm 1

85 (a) (b) [011] 0.5µm 0.2µm (c) (d) 200 [011] d=0.56nm (100) 1µm 2nm Fig (a) TEM image of the products. TEM image of a single Ga 2 O 3 nanobelt with (b) a width of 150nm and (c) a with of 1000nm. The insets are the corresponding SAED pattern recorded along the [011] zone axis. (d) HRTEM image of a monoclinic β-ga 2 O 3 nanobelts.

86 (a) (b) (c) (d) Fig SEM images showing ther general morphology of as-deposited products grown with Au-coated Si substrate. (a) Side-view image, (b) plan-view image, (c),(d) high-magnification image.

(a) (b) [100] 100 002 1µm 5nm [010] (c) [010] (d) d=0.

(a) Low magnification TEM image of the nanobelts.

Corresponding SAED pattern recorded along the [010] zone axis).

(Inset: Corresponding SAED pattern recorded along the [101]

88 (a) (b) [100] µm 5nm [010] (c) [010] (d) d=0.28nm (202) [101] [010] 202 [101] 1µm 2nm Fig (a) Low magnification TEM image of the nanobelts. (b) TEM image of a single β-ga 2 O 3 nanobelt (Inset: Corresponding SAED pattern recorded along the [010] zone axis). (c) Low magnification TEM image of a piece of a wide nanobelt (Inset: Corresponding SAED pattern recorded along the [101] zone axis). (d) HRTEM image corresponding to an area enclosed by the square in Fig (c).

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95 (a) (b) Si substrate (c) (d) Fig SEM images of indium oxide deposits grown on Si(100) substrate at 350C when Ar carrier gas flow rate is 20sccm and O2 gas flow rate is 5sccm. (a) Side-view image, (b) plan-view image, (c),(d) highmagnification image.

96 (a) (b) (c) (d) Fig SEM images of indium oxide deposits grown on Si(100) substrate at 350C when deposition time is (a), (c) 5min and (b), (d) 10min. (a), (b) Plan-view image, (c), (d) side-view image.

97 (222) Intensity (arb. units)(444) Si-(004) 2θ ( deg.) Fig XRD patterns recorded from indium oxide deposits

98 (a) Intensity (arb. units) c (b) Cu Cu Energy (kev) [111] 62 Fig (a) Typical EDS spectrum and (b) side-view schematic drawing of a single 1-D materials.

(c) 100 nm 101 321 222 [121] (d) 2 nm d = 0.

perpendicular to the stem of the 1-D materials.

99 (c) 100 nm [121] (d) 2 nm d = 0.29 nm ( ) d = 0.72 nm ( ) Fig (c) TEM image showing the tip part of a 1-D material. The inset shows a typical SAED pattern taken perpendicular to the stem of the 1-D materials. (d) Lattice-resolved HRTEM image of the rectangular box marked in Fig. 6-4 (c).

(e) [111] 031 222 211 100 nm [213] (f) d = 0.

100 (e) [111] nm [213] (f) d = 0.32 nm ( ) d = 0.29 nm ( ) d = 0.41 nm ( ) 5 nm Fig (e) TEM image showing nanobumps residing along the exterior of a 1-D material. The inset is a SAED pattern taken perpendicular to the stem of the nanobumps. (f) Lattice-resolved HRTEM image corresponding to the rectangular box marked in Fig. 6-4 (e).

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17(1)-06.fm

17(1)-06.fm Krean J. Crystallgraphy Vl., N. 1, pp.14~18, 006 LP-MOCVD w ZnO ù Ÿw p Á yá * w w» w» l Structural and Optical Prperties f ZnO Nanwires Synthesized by LP-MOCVD Prcess Yung-Jin Chi, Jae-Hwan Park and Jae-Gwan