本文以穿透式電子顯微鏡、掃瞄式電子顯微鏡，配合X光繞射分析來研究脈衝雷射剝蝕凝聚ZnO/Zn之擬磊晶與藉其特定晶面發展之氣-液-固(VLS)鬚晶。
首先，利用脈衝雷射剝蝕金屬鋅靶材的方式，以玻璃基板承接，合成具特殊{10 1}擇優取向之纖鋅礦結構氧化鋅凝聚物，發現其藉由發展良好的{10 1}單晶或雙晶面，相互接合形成擬磊晶 (Artificial epitaxy)。在快速加熱/冷卻的效應下，使這些纖鋅礦結構氧化鋅凝聚物具有相當程度的殘留應力，且粒徑會隨著氧流量增加而降低。
其次，將這些具特殊擇優取向之擬磊晶於600oC進行恆溫熱處理後，凝聚物會以自催化的氣-液-固生長方式，形成棒狀的纖鋅礦結構氧化鋅鬚晶。分析式電子顯微鏡觀察中發現這些鬚晶沿著發展良好的{10 1}極化面生長，來降低靜電能和表面能，或以特定較高共位晶格密度之{11 1}雙晶面生長。
再者，利用脈衝雷射剝蝕形成金屬鋅顆粒，使其包覆具有發展良好{10 1}及{11 1}面的纖鋅礦結構氧化鋅凝聚物，然後將之置於600 oC進行恆溫熱處理後，在熱氧化的效應下，使其生長成錐形且具馬賽克狀{10 1} 及 {2 1}雙晶的鬚晶。這些鬚晶的生長方式可以歸類成一種非常態的氣-液-固生長方式，亦即利用纖鋅礦結構氧化鋅凝聚物的特殊接合雙晶面(coalescence twinning plane) ，並藉著底部熔融態的金屬鋅進行生長。
最後，利用電子束照射奈米級的纖鋅礦結構氧化鋅與金屬鋅之混合凝聚物，發現由於動態的格隙/空缺遷移、晶格參差與毛細效應等因素，促使岩鹽結構氧化鋅的成核，並產生纖鋅礦/岩鹽態的殼核結構。這樣的轉變是依循著椅型皮爾斯扭轉(chair type Peierls distortion)方式之晶向關係 (1 1)R//(0 11)W; [011]R//[ 2 3]W，並且額外將(001)R面沿著( 2 0)W平面旋轉38度，來達到較佳的(10 1)W/(1 1)R晶格匹配度。

Wurtzite (W)-type ZnO condensates showed preferred orientation {10 1} when deposited on glass substrate by pulsed laser ablation on Zn target in the presence of oxygen. Such an artificial epitaxy depends on the well developed {10 1} surfaces of the condensates, which enabled {10 1}-specific coalescence to form twin and single crystal regardless of the co-deposited Zn. The W-ZnO condensates have decreasing particle size with increasing oxygen flow rate and a considerable residual stress due to the combined effects of rapid heating/cooling and thermal/lattice mismatch with Zn following parallel epitaxy or (01 )W-ZnO//(01 0)Zn; [ 2 3]W-ZnO//[0001]Zn involving {10 1} slip (Part I).

In addition, wurtzite (W)-type ZnO/Zn composite deposit with preferred orientation {10 1}W-ZnO and (0001)Zn respectively on glass substrate in chapter I under Isothermal (600oC) atmospheric annealing caused self-catalyzed vapor-liquid-solid growth of rod-like W-ZnO whiskers with unusual habit. Analytical electron microscopic observations indicated that the W-ZnO whiskers extend along the zone axis of the well-developed polar surfaces {10 1} for a beneficial lower electrostatic energy and surface energy. Alternatively, the whiskers extend via {11 1}-specific growth twinning and/or coalescence twinning for a beneficial fair coincidence-site lattice at the twin boundary (Part II).

Furthermore, Zn particulates overlain with wurtzite (W)-type ZnO condensates having nearly orthogonal {10 1} and {11 1} facets were found to self-catalyze unusual tapered W-ZnO whiskers upon isothermal atmospheric annealing, i.e. thermal oxidation, at 600oC. Analytical electron microscopic observations indicated that such whiskers formed tapered slabs having mosaic {10 1} and {2 1} twinned domains. The tapered whiskers can be rationalized by unconventional vapor-liquid-solid growth, i.e. {hkil}-specific coalescence twinning growth from the ZnO condensates taking advantage of a partially molten bottom source of Zn and the adsorption of atoms at the whisker tips and steps under the influence of capillarity effect (Part III).

Finally, Electron irradiation of nano-size wurtzite (W)-type ZnO condensates with intimate mixture of parallel epitaxial Zn caused {10 1}W slip to form a single domain of rock salt (R)-type core and W-type shell. The two polymorphs follow (1 1)R//(0 11)W; [011]R//[ 2 3]W, i.e. chair type Peierls distortion with additional 38 degree tilting (001)R along the ( 2 0)W plane for a fair match of (10 1)W/(1 1)R, the same as one of the two paths for the back-transformation of R-ZnO into a lower crystal symmetry. The martensitic nucleation of R-type ZnO can be attributed to dynamic migration of interstitials/vacancies, lattice mismatch stress, and capillarity effect.

Contents
Preface I
Abstract V
Contents VII
List of Figures and Appendixes X
List of Tables XXII

Chapter I
{10 1} artificial epitaxy of ZnO on glass via pulse laser deposition
1. Introduction 1
2. Experimental procedure 2
3. Results 3
3.1. Preferred orientation of the deposit on glass according to XRD
3.2. Size and coalescence behavior of the deposits on glass by optical polarized microscopy and SEM
3.3. TEM observations of the condensates collected on carbon-coated collodion film
4. Discussion 7
4.1. Oxygen flow rate dependence of size, phase and considerable residual stress of the condensates
4.2. Preferred {10 1} surfaces for the W-ZnO condensates
4.3. Artificial epitaxy
5. Conclusions 11

Chapter II
{10 1} and {11 1}-specific growth and twinning of ZnO whiskers
1. Introduction 31
2. Experimental procedure 32
3. Results 33
3.1. Phases and preferred orientation of as-deposited and annealed samples
3.2. Occurrence of W-ZnO whiskers in annealed sample
3.3. Habit plane and twinning of W-ZnO whisker
4. Discussion 35
4.1. The effect of condensate shape on whisker growth
4.2. Twinning assisted whisker growth
4.3. Twin plane specification of the whisker
5. Conclusions 39

Chapter III
Tapered ZnO whiskers: {hkil}-specific mosaic twinning VLS growth from a partially molten bottom source
1. Introduction 54
2. Experimental procedure 56
3. Results 57
3.1. Results of PLA process
3.2. Results of annealing
3.3. Investigation of single tapered whiskers
4. Discussion 61
4.1. Scenario of tapered whisker growth from a partially molten bottom source
4.2. Twinning energetics and mass transport for the tapered W-ZnO whisker
4.3. Implications
5. Conclusions 65

Chapter IV
Electron irradiation induced rock salt type structure from ZnO/Zn intergrowth
1. Introduction 75
2. Experimental procedure 77
3. Results 78
3.1. As-condensed particles
3.2. Electron irradiation-induced transformation
4. Discussion 80
4.1. Condensation of dense W- rather than R-type ZnO nanoparticles
4.2. Bulk nucleation of R-ZnO from W-ZnO/Zn nanocondensates
4.3. Peierls distortion path selection
4.4. Implications
5.Conclusions 84
References 93

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