These are the top 10 most cited (per year) Service Design academic papers I could find.

The top 10

1. This is service design thinking: Basics, tools, cases, which is one of the most well-known books on the topic of Service Design, with 2581 citations per year.

2. How to design a service by the mother of Service Design G Lynn Shostack with 1885 citations per year.

3. Service design for experience-centric services with 1385 citations per year.

4. The service concept: the missing link in service design research? with 1290 citations per year.

5. Benefits of co-design in service design projects with 894 citations per year.

6. Multilevel service design: from customer value constellation to service experience blueprinting with 865 citations per year.

7. This is service design doing: applying service design thinking in the real world, the follow-up to the book that is in the top 1, with 839 citations per year.

8. Service design: From insight to implementation, the book that brought me to Service Design, with 684 citations per year.

9. Customer experience modeling: from customer experience to service design with 570 citations per year.

10. Human issues in service design with 414 citations per year.

A little note about that top 10

I've removed SOA principles of service design (the Prentice Hall service-oriented computing series from Thomas Erl) with 2126 citations per year, from the top 10 as this paper is about service-oriented computing platforms. The term "service design" is also used by in IT for ITIL Service Design which has the same name but isn't the same practice