Ph.D. dissertations are commonly believed to be broad compendium of the original research done by a graduate student in partial fulfillment of the requirements for the degree of Doctor of Philosophy. Basically Ph.D. thesis is usually a number of disparate chapters whose most significant feature is not the thoroughness of the experimental description but rather the width of the margins. Writing a PhD dissertation is the last sticking point in the student's escaping from the graduate school. This is his original research on a meticulous problem which represents his accomplishment of the PhD process. The results of this research will become public, so the topic of the phd dissertation is of core importance.
To choose a good PhD dissertation topic, you should first of all understand the topic's main intention. The PhD dissertation topic has to focus on a specific question or problem and keep the dissertation research well-organized. The other important purpose of the PhD dissertations topic is to grab and to keep the interest of the audience.
-should be fresh and original
-should correspond to your professional and personal interests;
-should present some interest for you, your adviser and research committee;
-should be sufficiently grounded and have certain theoretical basis;
-should be worth exploring;
Above all, you should remember that PhD dissertation topics have to interest their authors, otherwise they will never manage to do good PhD dissertations. Secondly, the PhD dissertation has to be focused on the research of some new and burning problem in order to make a significant contribution into the science.